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DIY – Add a Transmission Replaceable Inline Magnetic Filter

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Old 01-02-2011, 10:09 AM   #1
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DIY – Add a Transmission Replaceable Inline Magnetic Filter

WARNING: use this information at your own risk. If an inline filter is installed backwards, internal damage to the transmission may occur. And damage to your own human body can happen, if the car falls on you. Use care, use jack stands, etc.

I have installed an inline (external) magnetic transmission fluid filter, because the factory filter is internal to the transmission and cannot be replaced. My add-on filter has been installed now for about 3 months and 2,000 miles. When it is replaced, I will post a picture of the insides of the old one. The top screws off of the one I used, so it is easily disassembled for a look inside.

Scroll down to the second (BLUE) section HOW TO INSTALL AN INLINE TRANSMISSION FILTER in an Acura RDX for the HOW-TO in 7 easy steps.

NOTE: I have tried to understand and follow the forum rules for including web links (as below). All links are intended only for informational purposes, and not for advertising, etc. I found it easier to post links to existing web site pictures, rather than try to host pictures and insert picture links (sorry). I am just another DIYer trying to pass along some info on my own modifications to my own car.

These are the reasons why I added a replaceable inline transmission filter to my own car:

Most manufacturers use some kind of filter in their transmissions, including Acura and Honda. And this has been standard practice for 40 or 50 years. Really, the only thing that has changed is that the filters have been getting more efficient during that time. And now Honda decides that some transmissions are ‘magic’ and need no filtration? Or no replaceable filtration?

The Honda CR-V and Element and Acura TSX have a factory installed (replaceable) inline filter. These engines are 4-cylinders. Some Honda Accord V6s have an OEM filter canister on the top of the transmission, allowing the filter to be changed, even if most dealers swear there is no filter. The Honda Odyssey and Acura TL and MDX 2001-2 have a replaceable screw-on filter. Various other Honda and Acura cars have replaceable transmission filters, depending upon year and make/ model. Honda (and Acura) always uses an inline filter when a replacement transmission is installed, to catch the materials from the damaged transmission that was replaced.

So the ‘lowly’ CR-V has a replaceable transmission filter, but the RDX does not? Things like this really puzzle me. I have my own opinion about why, but that is grist for another post.

I have added an inline transmission filter to my RDX, in an attempt to improve the transmission reliability. I do not in any way mean to suggest that if you do not add a filter, that your transmission is going to fail prematurely. You must make that decision for yourself.

I note this information here, not to worry or ‘excite’ anyone owning an RDX, but simply to make people aware that all car manufacturers have some problems with certain models, from time-to-time. Acura is no exception. I do NOT wish to start yet another thread about possible transmission problems, but only to note that some problems have existed in the past. Please do NOT post any trans problems to this thread, as there are lots of other threads already existing on this forum, where you can learn more or get answers to your problems/ questions. I have no answers. Search the forum.

I am not certain if everyone is aware that certain Honda/ Acura model/ years have a much higher transmission failure rate than most models. Those models with high(er) transmission failure rates, typically have neither a (replaceable) filter nor a cooler (which the RDX does have). Or if the vehicle with the failed transmission has a filter, the forum poster does not typically know of the filter, or report that it has ever been changed. Many posters report that their dealer states that there is no filter, even when they (the car owners) are certain that there is one.

Note that Honda uses the same transmission in several different models from both Honda and Acura. Use the following links and posted information, to help you decide if adding an inline transmission filter to your RDX might be a good idea. My summary of the following links, is that many of the posters think that adding a transmission cooler (if there is not one) and fluid filter (or changing the existing filter), will extend the life of the transmission.

Have a look at this link for Honda ACCORD (page 12 shows a picture of an add-on filter):
or this one for factory recall of Honda 2003-4 Accord V6, Acura 2000-4 TL, and Acura 2001-3 CL coupes:
or this one for Acura TL transmission problem FAQs:
or this one for Acura 2nd gen TL (1999-2003) owner posts (76 pages):
or this one for Acura 2nd gen TL (1999-2003) owner posts (17 pages):
or this one for an Acura 2001 CLS owner:
or this one for an Acura TSX owner:

Yes, the RDX transmission does have an internal ‘filter’. Replacement requires disassembly of the transmission. In earlier versions of this 5-speed transmission, this filter could be replaced easily, as it was external to the cases (inside a removable cover). The RDX transmission filter is available for less than $15, P/N 25450-P4V-013, good luck replacing it.

No idea how efficient it is, but clearly the internal RDX filter does not remove (filter) small particles, as there are always particles on my drain plug. The RDX transmission also contains an internal magnet – again it cannot be replaced without disassembly of the transmission. Obviously it is not working too well, because at the first oil change my transmission drain plug was saturated with magnetic particles.

What happens when the RDX transmission internal filter and internal magnet are saturated?

My intent is to use a replaceable external inline filter on the RDX, to limit (additional) wear of the transmission due to clutch particles, and metal particles, which are not trapped by the internal filter and magnet (or the drain plug magnet). These clutch and metal particles can clog internal transmission fluid pathways.

All of the oil will (eventually) flow past an inline filter. The magnet in the drain plug will only capture those (magnetic) particles that fall to the bottom of the pan.

When I did the first drain (of 3 quarts) at 8K miles, the drain plug magnet was completely saturated. That is, it could not ‘hold’ or attract any more particles. If I had waited until the factory recommended severe service interval of 60K miles to do the first drain, any particles generated/ created after 8K miles would have just been circulating through, and wearing out the transmission. The magnetic drain plug was no longer functioning at only 8K miles, since it was already saturated. I wonder if the internal magnet is also saturated?

The particles generated by normal transmission wear, do not really directly cause additional wear on the transmission parts such as gears, etc. No, the problem is that the particles can jam and cause malfunctions in the solenoids, valves, fluid conduits, and other electronic parts of the transmission. And a solenoid is merely an electro-magnet, attracting those metallic particles directly. Abrasive wear of the solenoid bores and O-rings, causes internal leakage and lower line pressures (which increases clutch wear), leading to total transmission failure.

And all of the fluid, which is filled with these particles, is constantly flowing through all of the parts of the transmission. A magnetic drain plug is only going to capture ‘some’ of the magnetic particles, and none of the non-magnetic particles (clutch particles, copper, aluminum, lead, etc.).

There are several different Honda/ Acura web forums with posted threads describing problems with clutch materials clogging the transmission solenoids/ sensors and related metal lines/ hose internal filters. The Honda Accord V6s with screw-on replaceable factory filters seem to have fewer solenoid problems (than those cars without a filter).

TRANSMISSION FLUID CONTAMINATION STUDIES: _filters/power_steering_filter.html
Engineers John Eleftherakis and Ibrahim Khalil get quoted a lot, both online and in general publications like car/ truck magazines. Apparently they have been doing transmission failure mode studies of automatics due to contaminants for 30 years. The results of those studies have been published in various Society of Automotive Engineers (SAE) technical papers since 1990.

The following seems to be their basic conclusions (my interpretation of what I read from the February 2010 issue of FOUR WHEELER):

· Type 1 contaminants – from the manufacturing process. In the average transmission used for 100K miles, these represent 70-75% of the total. These are best removed by a drain-and-fill with filter replacement at 100 miles.

· Type 2 contaminants – from normal use of the transmission. These represent 25-30% of the total. Remove the break-in accumulation with a complete fluid flush and filter change before 5K miles. Obviously this is difficult when you can only drain 1/3 of the fluid at one time. Also somewhat costly. So use good filtration from new, and replace the filter often.

· Contaminant composition/ makeup – “51 percent steel, 21 percent copper (copper wool clutch linings), 11 percent aluminum, and 7 percent lead (from bushings). Some 82 percent of the particles are larger than five microns in size, though only 15 percent of them are larger than 15 microns. Some are as large as 400 microns.”

· Good filtration – this was the most surprising part for me. There is something called the ISO CLEANLINESS CODE. The later 3-digit code shows the particle count above 4, 6, and 14 microns in size. FORD likes a code-count no higher than 18/15/xx. However, since this is a ‘code’, the ‘18’ is not the actual count above 4 microns, but a range-count of 1,300 to 2,500 particles per volume. Not sure what the standard fluid volume is, but that is besides the point for me. I am simply interested in the size of the particles being counted, and the relative counts specified. This is because the average engine oil filter is rated at 25 microns, which is almost twice the highest transmission micron size ISO code rating of ‘14’ microns (as stated at the beginning of this sub-section bullet).

· Danger of High Contaminant Particle Counts – any particle count above 21/18/xx for any transmission is definitely a danger area. See previous bullet for explanation of particle count code.

I want my RDX transmission to last at least 200K miles.

So based on the information just above, it seems to me that fluid changes should be done more often than the car manufacturer specifies – at least near the beginning of the trans life. This is to get rid of contaminants rather than to replace worn fluid. And remember, doing only one drain on the RDX removes only about 3.5 quarts of the 8.5 quarts (with contaminants) in the transmission.

So use a replaceable filter with an integral magnet. The best (inline) filter available for a transmission is rated only at 25 microns for the paper/ screen element.

At least a magnetic can remove most of the magnetic smaller particles, which represent over 50% of the total contaminant particles. And the particles removed are down to micro-size. That ‘mud’ on your magnetic drain plug is all magnetic, even though there do not seem to be individual particles. I am always amazed when someone says there is no metal on their magnet, just some ‘crud’. That crud is all metal.

The FOUR WHEELER magazine article which I referenced above, and quoted from, tested several filters and methods of cleaning the transmission fluid of various vehicles. The Magnefine was one of the filters tested. This is the filter that I chose to use.

[picture of RDX transmission cooler lines]

· Remove the bottom front splash shield, a plastic plate, which connects the front bumper cover to the front sub-frame.

· Remove the transmission cooler line, that runs from the front auxiliary cooler part (12) (driver side in front of the air conditioner condenser), to the passenger side rear (bottom) of the radiator. This is actually two rubber hoses, connected in the center of the run by a steel line on a bracket (bolted to the top of the front sub-frame). In the diagram below this is parts (7), (3), and (8).

· Replace the two rubber hoses with aftermarket hose – 3 feet total is required. Leave the center hose/ tube bracket attached to the car, part (3).

· Insert an inline filter between the two hoses. Orient the filter so that it flows correctly. Check any included filter instructions, or any arrow printed on the filter.

· The fluid flow is from the auxiliary cooler to the passenger side (bottom) of the radiator, which contains a cooler/ heater internal to the radiator. That is, the flow is FROM hose (7) TO hose (8).

· Clamp the filter to the front of the OEM steel line/ bracket, part (3).

· Replace the bottom splash shield.

For those that like detail here it is:
It seems I cannot directly insert pics into this post. Besides, once I put everything back together, the filter cannot be seen from the bottom of the car. And from the top of the car, backside of the radiator, I could not get a good picture. Removing the bottom front plastic cover will take you only a few minutes. If you look at the area on the vehicle, it should be pretty clear what is required, and whether or not you wish to do this installation.

v Remove the bottom front splash shield, a plastic plate, which connects the front bumper cover to the front vehicle sub-frame. The plate is about 4 inches wide, and runs across the entire front underside behind the front fender cover.

Ø There are 13 total push-pins plus two Phillips head screws holding this plate in place. There are 8 short push-pins and 5 long push-pins. Keep track of where they go for replacement.
Ø There are two push-pins inside the right (passenger) side wheel well. Removal of the tire/ wheel is not necessary, if the car is jacked up (lowering the tire/ wheel).
Ø The two Phillips head screws are located at each outside end of the plastic plate. The sheet metal screws are screwed into speed clips on the front fender cover, so you do not need to fear over tightening them, and ruining a plastic piece. The speed clip can be replaced if the screw strips its threads.

v Find the transmission oil line which runs FROM the cooler in front of the air conditioner condenser, TO the right (passenger) side of the radiator (back side) bottom. This line is behind the radiator.

v In the center of this oil line run, is a bracket bolted to the center (front) of the vehicle front suspension sub-frame, just above the front vehicle jack-point. This bracket contains a short steel tube. A hose runs FROM the right side of this tube, TO the radiator transmission cooler. A second hose runs TO the left side of this steel tube, FROM the steel line exiting the trans cooler in front of the A/C condenser.

v Remove both these rubber hoses. Use long nose pliers to compress the outer OEM hose clamps, and slide them back on the hose. For the two clamps on the center bracket/ steel line, a Vise-grips can be used.

Ø When the radiator cooler hose is disconnected only about 5 ounces of fluid will drain. Use a drain pan under the car.
Ø When removing the hoses, gently twist the hose to break it loose from the steel line. Hold the hose with your fingers behind the steel line, not over it (which compresses the hose tighter as you try to twist it).
Ø When pulling on the hose, take care to support the steel line with your hand, especially where it enters the bottom of the radiator. The bottom tank of the radiator is plastic, easily damaged.

v Replace the two lengths of OEM rubber hose with new transmission cooler line. New hose clamps are required. The OEM clamps cannot be used. Save the OEM hose and clamps in case you wish to remove the filter at some later date. Those OEM hoses cost like $20 each, and the clamps are about $5 each.

v Insert the INLINE FILTER between the two new hoses. Make certain to observe the DIRECTION OF FLOW for the filter. It should be marked on the filter. The fluid flow is FROM the front mounted transmission cooler, TO the radiator right (passenger) side. Or from left (driver) to right (passenger) across the back of the radiator.

v Clamp the inline filter to the front of the original bracket (which contains the steel tubing). Use zip-ties. Cover the ends of the original steel tubing with rubber vacuum covers, to keep dirt out. You may wish at some future date to reinstall the original oil line hoses, and you do not want dirt in that center steel line.

v Measure the amount of fluid drained from the transmission hoses, and refill the transmission with that exact amount. Then run the car for a few minutes, use the gear selector to move through all gear positions, then let the car sit for about 5 minutes, and measure the trans fluid level. Top-up if required. Assuming that the car has been sitting for some time, remember that this will be a COLD reading. Take a HOT reading after driving the car, and checking for leaks.

Acura RDX fluid flow (see cooler hose picture) = transmission (output line) part (5) -> front cooler part (12) -> radiator cooler (inside the bottom of radiator) -> transmission (return line) part (10) -> transmission internal filter -> transmission pan

You SHOULD determine this flow direction for yourself. Most inline filters are directional, and will limit flow if installed backwards into the cooler lines. This will damage the transmission.

Determining the fluid flow direction is straightforward, if not exactly simple. I used some old (30 years old but never used) 3/8 inch ID fuel line in the procedure below. It is best if the hose has never had any fluid in it (never been used) to limit any transmission cooler line contamination concerns.

Ø Remove the hose from the radiator bottom right (passenger) side. Remove the other end from the center bracket on top of the vehicle suspension sub-frame.

Ø Attach a new line to the radiator connection, no hose clamp needed. Lube the hose end with trans fluid so that it slips easily over the metal pipe, and so that it can be easily removed when done. Run the other end into a tub, oil drain pan, or other container.

Ø Attach a new line to the center metal pipe, and run the other end into a different container.

Ø Start the engine, and let it run a maximum of 3 seconds.

Ø When I did this, the first time I turned off the engine just as it ‘caught’. That was enough time to force fluid through the 5 feet of hose connected to the center sub-frame bracket. But I was not certain that I was seeing fluid flow from this hose. So then I started the car and let it run about 4 seconds. That was really too long. It pushed 1/2 quart out the hose on the sub-frame bracket. And none from the hose connected to the radiator. So that determined the flow direction.

Ø NOTE: I got tired of working on this, and left things at this point overnight. When I looked the next day, about 2 quarts of additional fluid had drained, or probably siphoned out the center bracket hose. I would guess if I had disconnected the hoses, this would not have happened. It just meant more fluid had to be replaced in the transmission after the filter was installed.

[picture of RDX transmission outer case]

The internal fluid filter is part (3). Part (8) is the transmission output line to the cooler. And part (9) is the return hose to the transmission from the cooler/ heater in the radiator.

I did not feel that there was sufficient space to insert an inline filter into any of the existing OEM cooler hoses, for the size filter that I used. A smaller (shorter) filter might fit into one of the OEM hoses – see section below for various filters, for example the CARDONE brand.

If the vehicle is “new” (<5K miles), then the filter should be placed inline between the transmission, and the external cooler (located in front of the vehicle). This is the transmission OUTPUT line. This location protects both coolers from any debris generated by the transmission, as well as protecting the transmission. I did not think that this location is practical, and besides, my RDX has 15K miles.

If the vehicle is not new, then the filter should be placed between the secondary transmission cooler (inside the radiator), and the transmission. This is the transmission RETURN line. This is to protect the transmission from any debris already deposited in either cooler, especially if the trans has failed. This location would be mandatory if installing a replacement transmission. This is where Honda/ Acura installs an inline filter when replacing the OEM transmission with a remanufactured or new one.

Again, I did not think that this location was practical, as the return line from the transmission cooler back to the transmission is rather short and curved. I have no idea how Honda installs a filter in this line (when a replacement RDX trans is used). Maybe they use a smaller filter. Maybe a long hose is used and curved around when routed. I have seen pictures of this type of installation. But I feel that the curves have the potential to collapse the hose and restrict oil flow.

So I have located my inline filter in the location easiest for me to install – the location described in the installation instructions above (between the two coolers). My installation allows the replacement rubber hoses to be almost completely straight.

If my suggested filter location is of concern, because your transmission already has high mileage, you can flush the radiator cooler. It should be flushed in both directions: first in the reverse, then in the forward direction. Use two cans of aerosol cooler flush from an auto parts store, one can for each direction. After flushing, allow both hose ends of the radiator cooler to be open for at least an hour, This allows any remaining flush fluid to evaporate. Then do a final flush with a quart of transmission fluid.

I did a transmission (drain-and-fill) times three at 8K original miles. And I added the transmission filter at 15K miles. So I did not do a cooler flush.

I have used a MAGNEFINE filter, manufactured in Australia. Pictures and more information here:

This filter includes a by-pass valve which will open if the filter begins to clog with debris. The size is length of 5 inches and diameter of 2.5 inches. The filter is available with three sizes of hose ends: 5/16” (8mm), 3/8” (10mm), and 1/2” (12.7mm). The 3/8” size is required for the RDX.

This filter contains “a 25 micron pleated paper” insert, no percentage rating given. In other words, there is no statement as to how effective it filters at 25 microns. There is an internal magnet inside the filter. The web site claims removal of 99.97% of magnetic particles. Even with the by-pass valve open, all fluid still flows past the magnet.

This filter was purchased online for about $16 plus shipping. Only the filter and two regular screw-type hose clamps were included, plus written instructions and diagrams. There are many sites selling this particular filter. Some sites include two short lengths of rubber hose or other parts, for an additional cost – not needed for an RDX.

This same MAGNEFINE filter can be purchased from your local FORD dealer under these part numbers for $45 up to $100, depending upon the purchase of a KIT or individual filter. Also, one Ford dealer quoted me a lower price for the kit than the individual filter. So check all of the part numbers for price. There are also online sites selling under these same part numbers:

The MAGNEFINE filter can also be purchased from SEARS online, for about $32. It was not available at my local Sears store.

Some NAPA and Oreilly Auto stores also sell this filter, either as a NAPA number or CARDONE number 20-FLT2. It is not listed as a Magnefine filter. You would need to look at it to determine if it is actually a Magnefine or another brand.

Please note that my information on the following filters is limited. If you are going to use one of these filters, you will want to do further investigation as to the suitability for your use. This information is provided largely to indicate that the use of inline transmission filters is common for Honda/ Acura both as OEM and when a transmission is replaced, and also that aftermarket filters are readily available.

CARDONE – available from NAPA, Oreilly Auto (and others) as P/N 20-FLT2, This is a MagneFine filter, for about $22. This filter is still being sold (as of 12/20/2010) as old stock. It is being replaced as below, so check which one you want and which one you are actually purchasing.

Cardone has updated/ replaced this part number (20-FLT2)with Magna-Pure P/N 20-0038F. The new part number is a smaller aluminum (housing) filter, intended for a Power Steering System. The filter is size 3 inch by 1.25 inch diameter with 3/8 inch hose ends. Filter itself is only one inch long, by-pass design, with a serviceable (cleanable) magnet and internal screen rated at 130 microns. This filter is short enough that it might fit into one of the RDX OEM cooler hoses. Available online from, Summit Racing, Amazon, etc. for around $15-20 plus shipping. Look here for a picture:

For an exploded/ disassembled view/ picture, look here: revent_premature_system_failure.aspx

HASTINGS – available at auto parts stores in my area as P/N TF109, UPC 7 68370 02660 9, cost of about $10. The size is length of 4-15/32 inch by 2-5/32 inch diameter. There is a by-pass valve. I understand that this filter is manufactured by FILTRAN, but am unable to confirm this. The web site states that this filter is for 3/8 inch line, but will fit 5/16 inch line. If I could have found a micron rating for this filter, I probably would have used this filter. More information can be found at

The unique aspect of this filter is that the magnet is composed of a ferrite-embedded synthetic resin, and the magnetic field does not extend outside of the filter body. This is desirable if the filter is placed next to some engine or transmission component that is electronically controlled. Magnetic fields and electronics do not play well together. Such is not a concern with the filter location that I have used on my RDX. This filter design allows for simpler manufacturing and assembly, which may account for the cheapest price rather than any quality deficiency. The patent for the Hastings filter may be found here:

HONDA CR-V 2008-9 or ELEMENT 2003-9 or 2004-8 TSX – this is an inline filter between the transmission cooler and the transmission, P/N 25430-PLR-003. The cost is around $15 online, dealer retail is about $20. There is a clamp assembly for this filter, P/N 25431-PLR-000 and 25432-RZA-000 on CR-V 2008-9. I have no other information on this filter. Look here and scroll (way) down for a picture:

Or look here for an installation picture with bracket: http://www./forums/showthread.php?t=33349&page=12

HONDA ODYSSEY or ACURA CL or TL or MDX 2001-2P/N 25450-P7W-003. This filter screws into the side of the transmission so it probably is not practical to install as an inline filter. I think that this filter is only used on the 5-speeds and not any 4-speeds, but not certain. Price is around $45. There is more information here:

HONDA GENERIC P/N 06250-PAX-010 – this is an inline filter KIT, price around $70. Honda uses this kit when replacing an OEM transmission with a remanufactured or warranty transmission. And it seems that this kit contains the same filter part as P/N 25420-P24-A01below, when ordered separately as a filter. Not certain, but I think that this kit comes with a hose-barb part that screws into the female end, making the length another inch or so. In other words, the kit allows for either two hose connections, or one hose and one steel pipe connection (I think).

HONDA P/N 25420-P24-A01 – not sure which models this fits. Dealer price is around $70. Size is length of 4 inches by 1 inch diameter. Hose barb of 10mm (3/8 inch) on one end, other end is female-threaded M14x70mm with 1.50 pitch, for use with a crush-washer, to screw onto a steel pipe connection. I do not think this part number comes with the optional barb for the female ‘screw-on’ end, so you may want to use the kit part number instead: P/N 06250-PAX-010

WIX POWER STEERING/ TRANSMISSION FILTER – available at auto parts store as P/N 58964, manufactured by FILTRAN, cost of about $15. The size is length of 5 inches by 2.4 inches diameter. There is an internal magnet and by-pass valve set at 4.8 psi. The filter is rated at 25 microns, with a burst pressure of 200 psi.

The filter hose ends are listed as 5/16 inch (8mm). That might be too small to work on the RDX, which uses OEM 10mm ID hose.

Something to consider is how much restriction an inline filter might cause, even with the by-pass valve open. As for any flow concerns, as soon as you disconnect the OEM RDX hose to the radiator, you will see that the hole in the RDX steel line is actually only 1/4 inch/ 6mm (or less) ID.

The only filter, of those listed above, which states a flow rate is the WIX at 2-3 GPM (gallons per minute). When I checked the fluid flow direction of the lines on my RDX, it pumped 1/2 quart in about 4 seconds (at idle). That is about 7.5 quarts per minute: 60 seconds / 4 seconds = 15 x 1/2 quart = 7.5 quarts = almost 2 gallons per minute.

The MAGNEFINE claims no flow restriction with the bypass valve open. And this filter is used by FORD and other car makers when a transmission is replaced, to clean up the debris left by the original failed transmission. It also (was) included by CARDONE with their replacement/ rebuilt Power Steering Pumps. That was my primary reason for choosing the MAGNEFINE filter.

Also, Acura and Honda require that an inline filter be used when replacing a transmission. And when replacing a damaged Honda transmission, the original inline filter must be returned with the failed transmission, for analysis. One source I have read stated that when a Honda replacement transmission is ordered from HEC (Howard Engineering Corp.), a Magnefine filter is included with the transmission:

I am not concerned about flow rates using the MAGNEFINE filter in my RDX, for the reasons given above.

Any inline filter that you use should be clamped or somehow attached in place, to prevent it moving about and causing stress to the line connections, or abrasions to the filter itself. Most filters have plastic cases, which in theory would eventually wear through from rubbing.

I wrapped my MAGNEFINE filter in a small sheet of thin rubber (craft store), about the thickness of an old tire inner tube (which would also work). I used small zip-ties to hold the rubber sheet around the filter. Then I used large size zip-ties (two) to attach the filter to the mid-run hose bracket with the OEM steel piping, mounted to the top of the front suspension sub-frame. By mounting the filter to the FRONT of the bracket, the filter fits into a sort of shallow V-shape and is held firmly in place.

While the filter cannot be reached without removing the plastic bottom spacer, I felt this location was better than on top of the pipe-bracket, because of the two bolt heads which mount the pipe-bracket to the welded bracket on the sub-frame. I also do not think that the hose routing would work with the filter on the top-back of this bracket.

The Magnefine filter label states to replace the filter once per year or 12K miles. The installation instructions state to replace the filter every 30K miles. Confusing. The first time I will probably replace the filter after one year, and open it and look inside. The filter top screws off, so it can be examined inside.

It is very important that the replacement hose you use should meet the SAE J1019 specification at a minimum. The SAE J1019 specification is: a temperature range of -40 to +300 F, and a maximum WP (working pressure) of 217 psi. The J1019 spec is for transmission and engine lubricating hose. Do not use fuel line or other type of low pressure hose.

I used GATES brand 3/8 inch ID hose purchased from NAPA. 3/8 inch is 1/2 mm less than 10mm, which is the OEM Acura RDX hose size. I used 3/8 inch ID hose rather than 10mm hose, because it fits tighter onto the Magnefine filter, and still fits over the 10mm RDX steel pipes. Besides, millimeter hose is not available locally to me, except through Honda.

The Gates hose cost around $4 per foot, and I used 3 feet. Probably only two feet are really required, but better a bit extra for the small price. This hose has printed on it TRANSMISSION COOLER LINE HOSE SAE J1019 400 psi WP, with a number CS071110, which I have no idea what the number means as it does not seem to be a part number. There is also printed on the hose GATES CORPORATION.

The Gates part number is P/N 27059 for 25 feet of hose. I do not know the NAPA part number, which is NOT the same as the Gates number just given, since the NAPA supplier is not Gates direct. I understand that it is also available from O’Reilly Auto P/N 27059, although my local store did not have any.

The Gates web site specifies this hose has a working pressure of 400 psi and a burst pressure of 1600 psi. The inner hose is nitrile, with fiber braid, and a hypalon cover. The working temperature is 300 degrees F.

Goodyear also makes a good transmission line cooler hose, which is made of CPE (chlorinated polyethylene) with a nylon textile outer cover for abrasion resistance. I like this hose better than the Gates hose, but it is not available to me locally. The Goodyear hose also meets SAE J1019, and has a 400 psi WP.

I used plastic spiral wrap in size 3/4 inch, purchased from NAPA as P/N 784 678. This wrap was used on both the hose replaced on the driver side of the vehicle, as well as the return line hose from the radiator back to the transmission. These two hoses are very close together with the new routing, and look like they will touch with only slight movement.

The OD (outer diameter) of the Gates hose is smaller than the OEM Acura RDX hose. Therefore, the OEM hose clamps cannot be re-used. The Gates hose is about 5/8 inch OD, or about 16mm.

I used ABA brand size 3 clamps, made in Sweden, purchased from my local Mercedes dealer. They cost around $3 each, and I needed four. These are fuel injector line clamps, with rolled edges and no through holes or screw-slots to cut the hose. They have a slotted hex head screw, so I used my 1/4 inch drive ratchet to tighten them. That was mostly for convenience, as it was easier to get a socket and extension into place rather than a blade screw driver. Just be careful to only tighten until the hose starts to compress, and do not over tighten. For a picture of this clamp, look here:

Another choice would be a NORMA clamp, part number N 102 582 01 from the VW dealer. This clamp has a range of 12-22 mm. These cost almost $5 each, and are really too large for the Gates hose. They would probably work on the OEM RDX hose which is about 18mm OD. But this NORMA clamp is the same size as the worm clamps provided with the Magnefine filter. Yes, that means that I think that the Magnefine provided clamps are also too large.

There is a smaller NORMA constant-tension clamp in 11-17mm size. I purchased these from the Mercedes dealer, also about $3 each. Sorry, I have no part number for these. They were in “open-stock” at the dealer. The parts persons said that the MB mechanics use these as replacements. These are slightly different from the VW part, as they are temperature-variable “constant-tension” type. I felt that these were still a bit too large, but would still work on the Gates Transmission hose. I just felt that the ABA size 3 clamps were a better fit.

I will be using these smaller NORMA 11-17mm clamps on the 3/8 inch ID hose when I install a Magnefine filter on the power steering line of my 1998 S-10 Chevy Blazer. The Gates Power Steering Hose I purchased has a slightly larger OD than the Gates Transmission line. I do not know why the hoses are different. I suppose Gates felt that the applications called for different hose. For a picture of these NORMA constant-tension clamps, and how they should be installed, look here:

Finally, there are two different Mercedes clamps which are 17-22mm: P/N 916 002 017 000 and P/N 005-997-27-90. Again this is too large for the Gates Transmission Cooler hose. These are also fuel line clamps, official Mercedes with the star stamped on the clamp, hence the $5 each price, $2.40 wholesale price (when I asked). The first clamp N916… has a Phillips head screw. The second clamp N005… also has a Phillips head screw, but the screw head is also a hex (will take a socket). Nice clamps, wrong size for this project.

I believe in safety wiring everything of a critical nature. It is easy to safety wire a slot-screw hose clamp, by running the wire though the screw slot and around the screw housing. But this requires that you actually have sufficient access to get both of your hands on the clamp. This is not possible on the clamps on the radiator and cooler connections, only on the filter clamps.

While the ABA clamps are much less likely than regular worm clamps to loosen, I still feel it is a good idea to “safety” the screws. And it is really easy to do. Simply apply a ‘gob’ of clear silicone sealer to the area under the screw head and on the clamp screw-slots. Once this sets, the screw will not loosen. And to remove the clamp, simply pry out the silicone sealer with a screwdriver tip.

By-the-way, this works with any other screw-clamp location. I use this on the clamps on the engine air intake hoses, and then I do not have to over tighten them, worrying that they will loosen. The screw heads on these clamps are Phillips, so safety wire is not practical (without drilling the screw heads).

To protect the unpainted ends of the steel pipe on the center sub-frame bracket, apply silicone dielectric grease, then push on vacuum line covers. The covers will also keep dirt out of the steel line. The covers will eventually crack from the heat, and fall off. Check every year.

Most auto parts stores will have vinyl vacuum line covers, in a kit of various sizes. Of course, you will need 3/8 inch size covers. Vinyl will not withstand the heat behind the radiator for long, however, so you will need to check them every year and probably replace.

Rubber vacuum covers are better for the heat. I found mine at a local store that sells terminal connections and bolts. They cost $0.20 each for 10. The actual ID is 1/4 inch, and they stretch to fit. A place that sells automotive type fasteners to auto body shops will probably also have this item. Check your Yellow Pages under BOLT or FASTENER.

NOTE: small size vacuum rubber covers are perfect to fit over brake caliper bleeder screws, after they are lost. The OEM Acura ones cost like $4 each (crazy).

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Old 06-25-2011, 02:01 AM   #2
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Installation pictures

Here are some pictures. When I did the original installation, I was in a bit of a hurry. A couple of weeks ago I had to remove the splash guard (to install a Power Steering Filter), so I snapped these.

The filter is located in front of the front frame member, and behind the radiator, at the bottom. It is completely covered by the Splash Guard, which must be removed to install and replace the filter. Now that I have done that a couple of times, I can remove the guard in about 10 minutes. The filter is zip-tied to the sub-frame welded bracket, to which is bolted the original cooler line hose pipe (#3 in the diagram below).

I used this filter for the reasons given in my original post. More information on this filter in my original post.

This filter includes a by-pass valve which will open if the filter begins to clog with debris. The filter size is length of 5 inches and diameter of 2.5 inches.

These installation pictures are from my own 2009 RDX. The filter is covered with a thin sheet of blue rubber/ vinyl, for shock/ abrasion protection. The zip-ties do not hold it perfectly in place as the bracket is flat, and the filter is round. The filter can move just slightly when the car hits a bump.

Reference the Splash-Guard diagram above. The Splash Guard is held on with two Phillips-head sheet metal screws (part #15), one on each corner of the car, screwed into a speed-clip (part #16) on the front bumper cover. Then, there are two sizes of body-clips (parts #17 short and #18 long). The longer clips are used where there are three (3) rather than two (2) body part layers to be clipped together. Or make note of the locations when removing the clips.

The body-clips tend to pack with mud/ dirt in the open end (opposite the button head). Unless this dirt is cleared, the button top does not want to ‘pop’ up. Since the clip open end points upward, it is necessary to flush water behind the radiator, from the top of the engine bay, toward the bottom. Look under the car to see where the body-clips are located. Use a low pressure hose, not a car-wash hi-pressure wand. Do not spray directly onto the electrical connectors on the radiator fans.

Use a screwdriver blade to lever-up the button top. Look on the button head. Pry at one of the two molded lines. Otherwise, you will be levering on the metal insert, which will likely break the clip. They cost almost $3 each to replace.

After removing the clips, soak them in a container with soapy water, then rinse and ‘shake’ dry – they do not need to be completely dry. Put a dab of silicone (dielectric) grease on the metal insert. That will keep the insert from rusting, and help keep dirt out for your next removal.

NOTE: the parts diagram which I looked at says there is only ONE #18 long clip used on the Splash-Guard, but that is not correct. Count how many of each length you remove, and notice that there is only a small difference in the length between SHORT and LONG. But there is enough difference in length to matter during re-assembly.

I have safety wired the drain plug. I did this so that I could lower the tightening-torque on the plug, to limit wear on those aluminum threads in the transmission. I have never had even a drip at the lower torque level, whether I use the OEM aluminum washer, or a copper aftermarket washer. I can purchase the copper washers from my local auto parts place, and I generally use them 4 or 5 times each before replacement, because they are softer than aluminum.

For more pictures and information, check Post #7 of this link:


Last edited by dcmodels; 06-25-2011 at 02:11 AM.
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Old 07-18-2011, 12:16 AM   #3
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REPORT (1) on AFTERMARKET inline filter after 2500 miles of Use

My goal is 250K miles (400K km) for the transmission in a 2009 RDX, which is operated under moderately severe conditions. I do not believe that following the MID (multi-function indicator display/ Maintenance Minder), or the additional severe service requirements in the Owner’s Manual, will achieve this goal. I believe that adding a replaceable inline magnetic filter is required, as a minimum.

The additional information provided below, is by way of explanation for why I added the aftermarket inline magnetic filter. I have only added the inline filter at this time, so I have no additional information concerning the other topics below.

I have not replaced or examined (internally) the inline filter that I installed. I did a drain/ fill at 2,500 miles after installation. The filter magnet is definitely removing metallic particles, based upon the lower-amount of metallic particles found on the transmission drain plug. This is compared to particles on the drain plug at previous ATF drains.

But there were still some particles on the OEM drain plug magnet. One reason is probably that only a small percentage of the trans pump output is re-directed to the trans-cooler circuit, and hence to the added inline filter. So at each pump-cycle, most of the fluid is dumped back into the trans-sump, and any (magnetic) particles are attracted to the drain plug. Also, based upon my maintenance cycle (before adding the inline filter), and the amount of particles found on the drain plug magnet at each cycle, the trans is producing metallic particles at a rate that is simply greater than the added inline filter can remove completely.

I cannot comment on non-metallic particle filtration, until the inline filter has been removed and opened. I will not do this until around 12K miles or 1-year (maybe Oct 2011).

This log is provided to give an indication of just how much wear particles are being generated by the RDX transmission. Each ATF drain and fill replaced 4 quarts of fluid, plus or minus a couple of ounces. There is no typo here, a full 8 (eight) drain/ fills were done.

And the transmission is generating a lot of wear particles, because of the very soft shift (high clutch slip), a result of the highly friction-modified Honda non-synthetic ATF-Z1. Friction modifiers (FM) in ATF control the amount of slip allowed for the clutches, sort of like FM in a limited slip differential (which also contains clutches).

07,875 miles: 22 Feb 2010, 3 drain/ fill, magnet saturated
10,820 miles: .. Apr 2010, 1 drain/ fill, magnet moderate
15,093 miles: 09 Oct 2010, INSTALL INLINE FILTER
15,428 miles: 30 Oct 2010, 1 drain/ fill, magnet heavy
17,620 miles: 10 Mar 2011, 3 drain/ fill, magnet light

I waited 500 miles after installing the inline filter at 15,093 miles, before doing another drain/ fill. That allowed the inline filter to clean-up the existing old ATF. At 15,428 miles I did another drain and cleaned the drain-plug magnet. Than I checked at the following drain (at 17,620) to see if the new filter was catching all of the particles, or if some were still being deposited onto the drain-plug magnet.

SATURATED means that the magnet was completely covered with particles, so thick that when the plug was removed, the mass began to ‘drip’ off of the magnet. That is, the magnet was not strong enough to hold the particles in place. The mass looked like sludge, black and thick.

LIGHT means that only one half of the magnet had a moderate covering of particles. The drain plug is inserted horizontally into the bottom of the transmission. So the magnet is also positioned horizontally. Only the top half of the magnet, full length, had particles on it. The bottom half was completely clean. Yes, it looked sort of strange.

The OEM trans drain plug magnet can only capture some of the wear particles, the magnetic (metal) ones that fall into the bottom of the trans pan. Clearly these particles are not being filtered by the OEM transmission filters.

As wear particles begin to build-up in the ATF, the particles themselves begin to cause more wear from abrasion. That is called a cascade effect, and it increases faster-and-faster. And at some point, the transmission internal filters, which cannot be replaced, become clogged, pump line-pressure drops, and the trans clutches burn-up. Line-pressure is what holds the clutch-packs engaged.

Also, remember that the electrically controlled valves are nothing more than an electro-magnet, which attracts the steel wear particles. The valves/ solenoids can jam from the particles, affecting shift quality, or even plug-up and reduce pressure to the clutches, causing them to burn.

Basically, severe service is many short trips, in temperature extremes, so that the oil (engine, transmission, differential, etc.) does not reach normal operating temperature. This RDX is driven 95% on trips under 10 miles (office commute), including 25% of the total trips under 2 miles (grocery, mall, gym, COSTCO, etc.). Each trip is separate, as the driver does not understand the concept of trip-consolidation (hope my wife does not read this). Temperature is in the 90s during the summer, and in the 20s during the winter.

Consider: if a car is driven 10 miles across town, and a stop is required only once each mile, then the transmission is shifted more than 50 times – 3 up and 3 down per stop/ mile times 10 miles. And if you drive like a maniac (who me?) so that all 5 gears are used (up/ down), then there are over 100 shifts. And the torque converter never locks-up (constant slippage/ clutch wear). Whereas in 10 miles at constant speed on the freeway, the torque converter locks, and there are zero (0) shifts.

Each transmission shift wears away a tiny amount of clutch material, just like a manual transmission clutch does. Clutch face material is finite (limited), and once gone, the transmission must be rebuilt.

The MID is supposed to consider and accommodate severe service into its reporting. But that is only for the engine oil. The other system fluids are supposed to be replaced at more frequent intervals than the MID reports, if the vehicle is operated under abby-normal (severe) conditions

The RDX Owner’s Manual (OM) defines severe service for the transmission as:
“Driving in mountainous [ed: UTAH] areas at very low vehicle speeds [ed: city commute] or trailer towing results in higher transmission and transfer fluid temperatures. This requires transmission fluid changes more frequently than recommended by the Maintenance Minder. If the vehicle is regularly driven in these conditions, change the transmission and transfer fluid at 60,000 miles (100,000 km), then every 30,000 miles (48,000 km).”

A 1998 Chevy Owner’s Manual (OM) has a more detailed definition of severe service (than the RDX owner’s manual). The [edits] and emphasis were added by me.

“If the vehicle is driven under one or more of the following [conditions], change the Automatic Transmission oil and filter every 15,000 miles:
Ø In heavy city traffic where the outside temperature regularly reaches 90 degrees (F) or higher
Ø In hilly or mountainous terrain
Ø When doing frequent trailer towing [ed: not going to happen with this RDX]
Ø Uses such as found in taxi, police, or deliver service [ed: does taxi service for school kids count?]
Ø If you do not use your vehicle under any of these conditions, the fluid and filter change should be changed every 50,000 miles”[ed: quite a difference from severe service isn’t it?]

Yes, it is true that current (circa 2011) model GM vehicles suggest longer drain intervals for their transmissions (than the above). But then, current GM vehicles are using semi-synthetic ATF Dexron-VI. Honda ATF-Z1 (obsolete) and DW-1 are both just petroleum based non-synthetic oils – check the MSDS on either oil for yourself. And also note that GM has had its own transmission problems with these longer drain intervals.



There are two internal filters, plus an internal magnet (not the drain plug magnet), in the RDX transmission. These cannot be replaced or serviced, without transmission disassembly. There are also filter-screens on the control solenoid ATF flow-pipes. Those screens can be cleaned or replaced by removal of the solenoids (not easy with the trans in situ).

The pump intake (suck side) filter is called a STRAINER, with good reason. Modern pump intake filters average around 100 – 150 microns, otherwise the pump cannot pull (suck) enough ATF to provide the required output line-pressure. The RDX strainer seems more of a screen, so it may be as poor as 200 microns. As a reference, a cheap engine oil filter is typically rated at 40 microns, an expensive oil filter is rated at 10 microns.


The cooler system filter is located at the output of the cooler system. That is, ATF is filtered only after it has passed through both the transmission air-cooler (located in front of the radiator), and the ‘heater’ (located inside the radiator). If this filter becomes clogged, its built-in pressure by-pass valve opens, and it no longer filters anything.

The aftermarket inline filter that I added is upstream of the OEM cooler system filter. Hopefully, it was installed early enough (low miles), that the OEM cooler-system filter can never become clogged.

Here is a picture of the OEM filter. I bought one out of curiosity. No, I have no hope of using it. Compare the size of the OEM filter with the aftermarket inline filter. The OEM filter is 60% the size (by volume) of the aftermarket filter. That means the aftermarket filter has a much greater filter area, plus it can be replaced periodically.

This magnet is located inside the bottom of the Torque Converter Case, just above the ATF Strainer. It is not listed as a replaceable part. Anyway, based upon the amount of particles I see on the OEM trans drain plug magnet, the internal magnet got saturated and stopped working very early. I can only hope that it is not located in some significant position that is supposed to be protected.


There are some online threads (including some in this Acura forum) where TL, TSX, Oddessy, Accord V6, etc. owners have been cleaning and/ or replacing these screens, as well as the solenoids. Or you can at least check the solenoids against the FSM (factory service manual) specifications (resistance in ohms). The two solenoids on Honda/ Acura transmissions for the past 10 years look similar, although the part numbers (and prices) differ. This includes the RDX models.

The picture from the RDX service manual shows just how small the screens/ filters on the solenoids really are – only 8mm diameter. That is why the screens are so easily clogged. Note that all of the solenoid pipes have filters: parts 1, 2, 3, 4, and 5 in the diagram shown above.

Some owners are servicing the solenoids because some models have suffered higher than normal trans failure rates. The screens are clogged, and the solenoids are jammed from particles or fluid varnish/ sludge – change your ATF more often? This service is being performed between 50K and 100K miles.

My assumption is that if an ATF inline filter is added at low enough miles, and the ATF is changed regularly, this procedure will not be required on an RDX (in order to reach 250K miles). Or maybe I will check the screens at 100K.

A/T service done... DIY (G1 specific) coming up! [ed: cleaning the solenoids – this is for a G1 Acura Legend, not an RDX, the screens are different. Plus you can just buy new RDX screens rather than clean them. But the cleaning process for the solenoids themselves is of value, plus some good pictures] r

Honda did not build the RDX transmission to last forever – it has a ‘design-service-lifespan’, just like every other part on the vehicle. The only thing that we know for certain is that Honda expects the RDX transmission to last as long as the warranty period. So the internal filters probably will last at least that long before they clog-up. But what if you want your transmission to last much longer than the warranty period, say, 5-times the warranty period?


Note that a G3 (3rd generation) 2004-2006 Acura TL transmission has a replaceable cartridge filter, similar to the RDX internal cartridge filter. The TL filter in the picture above was replaced at 108K miles, after two or three ATF fluid changes during those miles. Looks pretty much like the RDX filter, doesn’t it?? Different part number though.

Check the following post for details.
5AT Filter Cartridge – posted thread ter

An Acura G2 1991-1995 Legend transmission has a replaceable ATF pump strainer, similar to the RDX pump strainer. Drop the pan and replace the strainer. So yes, Acura used to think that the strainer can clog, and should be capable of being serviced. Check the following post for pictures and a DIY.

G2 Transmission Solenoid Screen & Valve Body Cleaning [ed: listed for the pictures of the ATF pump strainer] er

I was finding considerable swarf/ metal on the OEM drain plug magnet in only 5K miles, before adding the inline filter. These three suggestions are offered in order of cost effectiveness.

ATF-Z1 (obsolete) is not a synthetic oil, and neither is the new replacement ATF DW1 – check the MSDS (manufacturer safety data sheet) for yourself.

Draining ATF removes any particles (suspended) in the ATF. For example, doing a single drain every 5K is much preferable to doing two (or even three) drains at 10K intervals. This also leaves less older fluid in the trans for a shorter period. If these intervals seem very short, simply do a drain now yourself, at whatever your current mileage is, and check how much swarf is on the drain plug magnet.

Every car manufacturer other than Honda, has been using synthetic ATF for at least 5 years now in their transmissions. Synthetic ATF is used to reduce transmission wear, varnish, and sludge – and to lengthen ATF service life. Honda ATF-Z1 is not known for its long service life. Failure to change ATF at regular intervals can cause valves to seize from varnish (high heat) and sludge, or jam with wear particles. At least the RDX has a trans cooler, something many other Honda vehicles do not have.

A single drain of 4 quarts removes just under 50% of the ATF. According to the service manual, the trans holds 8 quarts plus 6.4 ounces (8.2 quarts). Removing 50% (single drain) of the old fluid at short intervals is better than removing 75% (two drains), or 87.5% (three drains), at longer intervals.

The RDX Owner’s Manual says: ”change the transmission and transfer fluid at 60,000 miles (100,000 km), then every 30,000 miles (48,000 km).” The opposite is much more logical. Change first at 30K then at 60K intervals. That would remove the break-in and early wear particles first, so that the lowest level of wear particles is maintained during the life of the transmission, preventing a cascade effect of wear.

Also, do we interpret the Owner’s Manual literally, and do a 3x4 drain and fill (change the transmission and transfer fluid)? After all, change the transfer fluid means change all of it. So does change the transmission fluid mean change all 8 quarts, or just the 4 quarts that drains directly?

See more on this topic above, where the screen filters are discussed.


To be done as a preventative maintenance measure. People are doing this at around 50K+ miles on TLs, Accords, Odysseys, etc. These switches are both mechanical and electrical in function. Mechanical parts are subject to wear from the trash (metal particles) in the ATF. Electrical parts do not last forever (my previous microwave-oven failed just beyond the 1-year warranty period).

These switches rarely fail ‘hard’ (suddenly). When these transmission pressure switches begin to fail, line pressure to the transmission clutches falls, the clutches burn, and you need a new transmission. The switches can fail so slowly that by the time you notice a (shifting) problem, or get a DTC (diagnostic trouble code), the damage is already done.

The same oil-pressure switches have been used on various Honda/ Acura transmissions for the past 10 years. For example, part numbers for the trans pressure-switches on a 2004 TL are exactly the same as for a 2009 RDX trans, even though the transmissions are different.

Very interesting conversation with my transmission builder on the TL – posted thread

A-110: DIY Guide to replacing 3rd & 4th gear pressure switch for 3G TL (2004-2006) – posted thread

Here is some Info on the 2G CL/TL transmission .. ATF filter change .. Solenoids [my ed: pressure switches not solenoids] ...ect – posted thread

Racing ATF – posted thread: see post #842 and #976

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Old 07-18-2011, 04:16 PM   #4
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Thought my posts were long-- sti's and Betty White... Holy jebus... Lol, I am still reading it. Very detailed write up.

You could also anty up and do a larger ATF cooler with a blower fan wire parallel with the rad fans. The filter media can do more harm than good if in the wrong hands, not the case here. If neglected it would impeed the flow, is there a bypass on this?
I'm 1/5 the way thru...

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Old 11-15-2011, 10:33 AM   #5
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Can someone please HELP!!!! Need to know how to go about changing a valve cover on a 98 Acura 3.0 cl. If you have pictures that would help alot. Thx u.
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Old 06-18-2012, 09:00 PM   #6
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REPORT (2) CHECK AFTERMARKET inline filter after 6200 miles and ONE YEAR

After one year and 6,200 miles, the aftermarket MagneFine inline filter was removed, and examined internally, to determine just what is happening.

My goal is 250K miles (400K km) for the transmission in a 2009 RDX, which is operated under moderately severe conditions. I do not believe that following the MID (multi-function indicator display/ Maintenance Minder), or the additional severe service requirements in the Owner’s Manual, will achieve this goal. I believe that adding a replaceable inline magnetic filter is required, as a minimum.

I removed the Magnefine inline filter and opened it up. The top screws off. I used two channel-lock pliers, the extra-large size. The top is sealed with an O-ring, so not much force was required to remove the top. The donut shaped thing is the magnet, and there were particles on both sides. The black ring on the white paper towel was where I cleaned the back of the magnet. Shown is the front side of the magnet.

The next picture shows the basic filter parts, after disassembly.

The next picture shows a Q-tip that I rubbed gently on the paper filter down 3 pleats. That is to illustrate how much material is collected on the outside of the paper filter.

The next picture shows a comparison of the Magnefine inline paper filter, compared with the actual Acura RDX filter inside the transmission (which cannot be replaced). Gee, they look about the same size don’t they? Except that the OEM RDX filter has only 1/2 or less filter medium, compared with the MagneFine paper filter. Note the spacing on the paper folds.

So guess what the OEM filter looks like inside your own transmission? How many miles since you last changed your ATF? Have you ever changed your ATF?

This log is provided to give an indication of just how much wear particles are being generated by the RDX transmission. Each ATF drain and fill replaced 4 quarts of fluid, plus or minus a couple of ounces, out of a total of 8.2 quarts.

And the transmission is generating a lot of wear particles, because of the very soft (smooth) shift, which allows some transmission clutch slip. Yes, this trans has several clutches (a clutch-pack) for each gear.

The soft shift is a result of the highly friction-modified Honda non-synthetic ATF-Z1. And the new DW-1 ATF oil, used on the last drain/ fill below, is little better than Z1. Friction modifiers (FM) in ATF control the amount of slip allowed for the clutches during a gear-shift, sort of like FM (in the oil) in a limited slip differential (which also contains clutches).

07,875 miles: 22 Feb 2010, 3 drain/ fill, magnet saturated
10,820 miles: .. Apr 2010, 1 drain/ fill, magnet moderate
15,093 miles: 09 Oct 2010, INSTALL INLINE FILTER
15,428 miles: 30 Oct 2010, 1 drain/ fill, magnet heavy
17,620 miles: 10 Mar 2011, 1 drain/ fill, magnet 1/2 heavy
17,880 miles: 24 Mar 2011, 1 drain/ fill, magnet 1/2 light
17,926 miles: 27 Mar 2011, 1 drain/ fill, magnet trace
21,260 miles: 22 Sep 2011, 1 drain/ fill, magnet 1/2 light, REMOVE INLINE FILTER

After installing the inline filter at 15,093 miles, I waited 300 miles, before doing another drain/ fill. That allowed the inline filter to clean-up the existing old ATF. At 15,428 miles I did another drain and cleaned the drain-plug magnet. Than I checked at the following drain (at 17,620) to see if the new filter was catching all of the particles, or if some were still being deposited onto the drain-plug magnet.

SATURATED means that the magnet was completely covered with particles, so thick that when the plug was removed, the mass began to ‘drip’ off of the magnet. That is, the magnet was not strong enough to hold the particles in place, once the drain plug was removed from the trans. The mass looked like sludge, black and thick.

1/2 LIGHT or 1/2 HEAVY means that only one half of the magnet had a covering of particles. The drain plug is inserted horizontally into the bottom of the transmission. So the magnet is also positioned horizontally. Only the top half of the magnet, full length, had particles on it. The bottom half was (almost) completely clean.

Yes, it looked sort of strange. I think that this happens partly because the north/ south poles of the magnet seem to be the top/ bottom of the magnet, instead of the two ends of the magnet.

About 4 ounces. And that is only an estimate.

When adding the filter for the first time, you will need to add a little ATF to account for the volume of the filter. Remember that the difference between the top and bottom holes on the transmission dip-stick, marking the ATF volume, is only 8 ounces. So the 4-ounces in the new filter matters.

I run my transmission 2-ounces below the top mark (hole) on the dip stick. That is a bit low so that I do not overfill when doing a drain & fill. But high enough that I can add the 4-ounces for the new filter, after the drain & fill, without worrying about over or under filling the transmission, before I have a chance to take a valid cold-reading.

To help me remember exactly how the trans dip-stick reads, I added the following to my own OM (owner’s manual) on page 344. The HOT diagram may not be exact, but I am an engineer, not an artist. Have a look at your own dip-stick, and draw up your own diagram.

For more information on taking a valid cold or hot transmission ATF level reading, you can check this thread, or search for other links on this forum:

LINK: Transmission Oil Level Reading and Oil Change COMMENTS:

Anyway, the main point here is that it is very important to carefully measure the amount of ATF drained, so that you can refill with that exact amount. Be aware that cheap cooking measuring cups from K-mart and the like can be off by 2-ounces in a 1-quart measuring cup. That means when draining 4-quarts, and using a 1-quart measuring cup, you can be off by either plus or minus 8-ounces on the refill. Not good.

Accurate measuring containers are available from photographic or chemical companies, and you can buy mail-order or online. Or you can calibrate any measuring container that you already have, with a cheap quart of oil from K-mart. No matter how cheap the oil, you can bet it will measure out to exactly 1-quart. That is what I did with one of my wife’s cooking Pyrex 1-quart measuring container (which I appropriated to replace the one she tossed out when cleaning the garage). The container is actually quite accurate, although the marks on the side are about 1/2-ounce thick, so I noted whether 1-quart came to the top or bottom of the 1-quart line.

The OEM internal (and non-replaceable) transmission filter does not filter out the smallest particles. That is why there are particles on the drain plug magnet. And the added Magnefine inline paper filter cannot filter out the smallest particles either. But it does have its own internal magnet.

However, only some of the fluid flows through the trans cooler circuit, and through the Magnefine filter, with each cycle of the trans pump. The rest of the fluid is pumped directly through the trans to operate it, and then directly back into the sump. Any particles fall to the bottom of the sump and are attracted by the drain plug.

But the wear particles are very small/ fine, so many particles remain suspended in the ATF. The Magnefine filter is there to remove the suspended particles. But this takes multiple cycles of the pump through the cooler circuit, to remove suspended particles in the ATF.

The end result is that some particles are captured by the Magnefine inline filter, and some are captured by the OEM drain plug magnet.

The label printed on the filter that I purchased online from a Magnefine supplier, says every 12K miles or once per year. The installation instructions say every 30K miles. Hose clamps were included, although I used my own clamps. The online price was $16, but with shipping, it is about the same price as from NAPA.

The label printed on the Raybestos filter that I purchased from NAPA, says replace every 10K miles or once per year. There were no installation instructions or hose clamps included. The NAPA part number is tranny p/n 1-8514 and my price was $25 plus tax. This is really an actual Magnefine filter. It says so right on the filter label, but check for yourself before paying. Without the part number, the idiot at NAPA could not find the filter.

Based on what I found when I looked at my own filter, I will be replacing the filter at 2-year or 15K mile intervals. If you are concerned about the Magnefine filter plugging, remember that it has a by-pass valve in the paper-filter that is basically the same as the by-pass valve in the OEM Acura RDX internal trans paper filter (I purchased one and looked).

It is my opinion that the OEM drain plug magnet is capturing particles mostly after the engine is shut-down, allowing the finest particles to fall to the bottom of the transmission sump. And that during normal engine/ trans operation, most of the wear particles are suspended in the ATF and circulating through the transmission, causing wear.

So filtering out suspended particles in the ATF is a high priority. That is what the Magnefine inline filter does. The OEM Acura transmission filter is at the end of the cooler circuit (inside the transmission), where the cooler line from the radiator bottom re-enters the transmission. The Magnefine inline filter is in the cooler circuit, so it is filtering any particles before the ATF returns to the transmission, and the OEM filter.

Eventually during engine/ trans operation, all of the ATF will flow through the transmission cooler lines/ circuit, so that the Magnefine inline filter has an opportunity to filter any suspended particles.

This is good, because sooner or later the OEM filter will plug, and the by-pass valve will open, so that it is not filtering at all. The Magnefine inline filter will continue to clean all of the oil circulating through the cooler lines.

I also note that the total amount of particles captured by both the Magnefine inline filter and the OEM drain plug magnet together, seems to be greater than the amount of particles captured by the OEM drain plug magnet alone, when there was no Magnefine inline filter installed.

That may not seem logical, but remember that the OEM drain plug magnet can only capture those particles that fall to the bottom of the trans sump. Any particles in suspension, or that fall away from the drain plug will not be attracted to the drain plug magnet. Its magnetic range is not really that large.

The OEM trans drain plug magnet is a ceramic type, not a neodymium type, hence its large size (for greater magnetism). Neodymium is 10 times stronger than ceramic, for the same size magnet.
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Old 01-14-2013, 01:12 AM   #7
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Of the 5 (five) MagneFine inline filters that I have used, the first 2 were obviously defective, 1 did not display any problems, and 2 are still in service (but show no signs of problems).

Two of the five filters that I have used were installed in my RDX Transmission Cooler line, and three were installed in the Power Steering return line. I am combining the results of filter use in both systems, here in this transmission thread, because all five of the filters used are exactly the same. I purchased 3 filters from one source (online), and two at a later time from the same local NAPA dealer.

I will give details on disassembly and examination of this filter, in a later post. However, if you are handy enough to install the filter, you should have no trouble with disassembly.

The filter top simply unscrews, and is sealed with an O-ring. Large slip-joint pliers or pipe-wrench will work, but may damage the filter. I am uncertain if the filter can be safely reassembled, without leaking. If it can be, that would seem to be a good idea – to disassemble, examine for any defects, and reassemble *before* installation on your vehicle. And if the filter has any defect at all, DO NOT use it. Better to ‘waste’ $25 by discarding a faulty filter, than to have your Transmission or Power Steering system damaged.

I have posted part of the following information, in my thread on Power Steering inline filter addition. But there seem to be 10 times the hits on this thread, so I am posting the following as a warning. I used a MagneFine filter in both the RDX transmission cooler line, and the RDX power steering return line.

The first MagneFine filter that I used in the PS line, was removed after 1-year and 7800 miles. It was leaking from the seal on the screw-on top, and had a defective by-pass valve. The fluid leakage was minor, and not obvious until the wheel-well liner was removed.

The filter by-pass valve was glued closed, from the manufacturer. Excessive glue from the paper cartridge had glued the by-pass valve shut, as factory original. When I disassembled the filter, it took at least 20 pounds of force to open the by-pass. The by-pass should not require more than maybe 2-pounds of force to open.

The second Power Steering replacement filter *also* leaked from the screw-on top, after 6-months and 2500 miles in the Power Steering line. The leakage of the second filter was greater than the first filter. It made a mess, but the actual amount of fluid was probably only about 3-4 ounces, as determined by the level drop in the PS fluid tank. I did not feel that any disastrous failure was imminent.

The third Power Steering replacement filter has been installed for 1-month and 500 miles. There is no sign of a leak at this time.

The first MagneFine filter I used in the Transmission cooler line lasted 1-year without a problem. The by-pass valve was not checked after disassembly. The current MagneFine filter in the Transmission cooler line was installed 6-months and 3500 miles ago, and is not leaking.

This is the filter from the PS line with the frozen by-pass valve. Note that in this picture there is no sign of a problem. That is why you *must* actually open the by-pass valve, to determine its proper function.

PICTURE: first filter

The next picture shows the various parts of the filter and its operation.

PICTURE: filter operation

The next picture, a cut-away of an actual filter, shows that the magnet is supported at the intake end of the filter. And that the magnet is separated from the paper filter, so that oil can flow completely around the magnet.

PICTURE: cut-away

If you look at the first picture in this post, you can see the fluid pressure by-pass valve. It is just a spring-loaded tightly fitting button, in the intake end of the paper filter canister.

THE BY-PASS VALVE WAS FROZEN (glued closed), when I disassembled the filter. It should only take <2-pounds of pressure to open, a trivial amount. When I pushed on it, it took perhaps 15-20 pounds estimated, to force it open.

PICTURE: by-pass valve SIDE

The reason for the frozen by-pass, is that too much glue was used to attach the paper filter material to the end of the metal cap. A drop ‘oozed’ onto the by-pass button, in one small area. The by-pass button was glued to the filter end-cap opening.

After it was forced open, the by-pass functioned easily, but the glue-blob would prevent proper sealing. Probably, the by-pass was not properly seated & sealed while the filter was installed on my vehicle. That means that the filter element was not properly filtering the PS fluid.

PICTURE: by-pass valve BOTTOM

The glue is only on the edge of the button. It can be seen in the picture just above, only because the button is retracted down inside the by-pass valve housing. Look at the picture at the beginning of this post. The glue cannot be seen. The top edge of the by-pass valve (button) was glued to the underside of the top end-cap of the paper filter.

PICTURE: excessive glue

I find this situation somewhat concerning, as I put another MagneFine filter just like this one back into the Power Steering line, and also a second one back into the transmission cooler line.

In theory, the by-pass should not be required, until the paper filter has become saturated (clogged). However, when the ambient temperature is below zero, and the transmission ATF fluid is cold, the fluid is also much thicker than when its warm. I do not know how to determine whether or not there will be some flow restriction, when the temperature is cold, and the by-pass does not open. So I think it is very important that the by-pass be functional, even when the filter is newer and there is not yet any flow restriction through the paper filter.

The MagneFine filter by-pass is exactly the same design as the by-pass in the RDX OEM internal transmission filter. I know, I looked (at an OEM replacement filter). Kind of makes you wonder, does it not?

I mean, what happens if the RDX transmission OEM non-replaceable filter should become ‘saturated’ and its by-pass valve does not open? Well, that is why I installed an inline MagneFine filter in the transmission cooler line. So that the MagneFine replaceable filter removes enough material, that the OEM internal filter never does get saturated.

The MagneFine filter screw-on top is sealed with an O-ring. This is what a leaking seal looks like. This picture is not my own filter, but taken from one of the links below, from another poster with the same problem. However, my own filter looked much like this, only worse. Fluid had dripped down from the filter, and all along the RDX right-hand rail of the front engine-cradle (sub-frame), and under the bottom chassis.

Since my PS filter was installed vertically, with the filter ‘top’ pointing down, it was very clear where the leak was from, and not from either hose clamp on the filter.

PICTURE: leaking top

PICTURE: disassembled filter/ parts

Ford sells (or did sell) a re-labeled MagneFine filter, both as a kit for installation with a remanufactured transmission, and as a separate filter, for individual installation. The following is a partial quotation with my added emphasis, from




LINK: Fords TSB Against Installing a Magnefine #2145470 - 01/20/1111:18 PM

Here are some links to posts which describe some of the problems others have experienced with the MagneFine filter. I cannot verify the accuracy of what has been posted – the links are provided as a reference only. Problems with Magnefine filters are not unique, but perhaps not common.

LINK: failed by-pass valve, opened only half way, causing flow restriction: post #6

LINK: failed by-pass valve, opened only half way, causing overheating: post #10, from the same person as the link just above

LINK: Re: Remanufactured OEM Ford Transmission 04 Navigator [Re: Trav] #2364607 - 09/01/1107:52 PM – quote from Magnefine for filter bypass specification
LINK: Re: Remanufactured OEM Ford Transmission 04 Navigator [Re: Trav] #2364894 - 09/02/1106:26 AM – leaking/ seeping seam of filter top

LINK: Re: Magnafilter & Magnefine [Re: Johnny248] #2208197 - 03/22/1111:59 AM – leaking filter

LINK: Trouble with Inline Transmission Filter 05-09-2012, 07:34 PM – leaking Magnefine filter

LINK: #1282159 - 11/13/0803:57 PMRe: Magnefine filter testi [Re: Donald] – leaking Magnefine filter, with pictures
LINK: #1283136 - 11/14/0802:45 PMRe: Magnefine filter testi [Re: Donald]

WHAT TO DO? about quality control:
Here are some things you can do. Let us consider each option in turn:

Ø Check that the MagneFine filter functions properly

Ø Replace the MagneFine filter in a timely manner

Ø Use another brand of filter

Open up the new filter and check the by-pass valve, BEFORE installing it. The MagneFine and Cardone filters are the only ones that I found, that can be opened without damage. No other filter allows checking the function of the by-pass. And some filters do not have a built-in by-pass function.

The MagneFine filter-top just unscrews, and is sealed by a rubber O-ring. So that it should be OK to remove and re-install the top before use, to look inside. But, since I have not actually tried this, I cannot verify that the MagneFine filter can be safely reassembled without leaking.

Do note that even if the MagneFine paper filter by-pass valve does open, that oil still flows over and around the magnet, continuing to remove any magnetic metal filings. And if the by-pass valve fails to open, so long as the paper filter is not clogged, there will be little limit to fluid flow.

Replace the filter within the time-frame (service-interval) specified by the manufacturer. Please note that my MagneFIne TRANSMISSION filter in service, as shown in a previous post in this thread, shows just how much debris the RDX transmission can produce. Note the service interval of that particular filter, as well as the Transmission service record for the particular RDX in which the filter was installed.

Basically, I am stating that my RDX transmission had the ATF oil changed at regular and very short intervals. There was not time for a lot of debris/ wear material to build up inside the trans case. If you have not serviced your trans for some length of time, I strongly recommend a 3x3 flush (per Honda instructions), _before_ installing an inline filter, and also, do _not_ exceed the MagneFine filter recommended replacement interval.

Any brand of filter with a by-pass, has the possibility that the by-pass will fail to open. And some filters do not have a by-pass, which is even worse. Only the Cardone and MagneFine Power Steering filters can be disassembled, to check that the by-pass functions properly. On the other hand, a filter that cannot be disassembled, is unlikely to leak from the assembly seam, as happens with the MagneFine.

Remember, nothing is ever perfectly manufactured. Every manufacturer of every product, has a certain QC (quality control) failure rate (bad product). That is why warranties are provided. Keep in mind the possible result of using a bad product. In the case of a Power Steering system, if the filter by-pass never HAS to open, there is likely no problem. But if the filter clogs and the by-pass FAILS to open, the Power Steering system can be damaged.

The Cardone Power Steering filter described in my original post, differs in design from the MagneFine. The Cardone filter is designed to be disassembled. This can be done before installation, to check for proper function. And it can be disassembled after use, to clean and reuse. I do not believe that the Cardone filter design would allow the by-pass function to fail. However, the Cardone magnet is ‘tiny’ compared to the magnet inside the MagneFine filter. Therefore, the Cardone filter should be serviced at appropriately shorter intervals.

Unfortunately, I would not use the Cardone filer as a transmission filter. When I posted my DIY for a TRANSMISSION inline filter, I included all of the various filter options that I found. I believe that any inline trans-filter can be used as a power steering filter (but not vice versa). The Cardone filter is specifically made for Power Steering use. But of course, you must decide for yourself.

I do not claim to have found every possibility for an inline Transmission Filter. But one thing I do note is that there are many *brands* of filters, that are just relabeled MagneFine filters. As best I can determine, the MagneFine filter is the most common, and most sold filter, available as an inline transmission filter.

I think that either 12K miles or 1-year is a safe interval to change the MagneFine filter, at least under the operating conditions of my own RDX. This is the interval(s) stated on the filter label.

I do not recommend a replacement time period of longer than 1-year, even for very short mileage, because the MagneFine particle filter is made of (treated) paper. Paper breaks down faster than a fully synthetic filter medium. This applies to service in both the Power Steering system and the Transmission system.

Remember, most engine oil filters have a recommended maximum replacement time limit of 1-year for synthetic media. Or as short as 3-months for oil filters using treated paper, the same type of medium in the MagneFine filters.

As only one example, Purolator currently offers three different ENGINE-OIL filters: Classic, PureOne, and Synthetic. The Purolator web site says the following:

Synthetic, wire-backed media + 99% efficiency + 27 grams capacity = 10,000 mile protection. [my edit: no replacement time frame given by Purolator]

Purolator PureONE oil filters should be replaced every 3,000 miles or 3 months depending on the driving conditions - or unless otherwise specified by the vehicle's manufacturer.

For low-mileage or highway driving, a Purolator Classic oil filter is the oil filter of choice.

Note the low replacement intervals specified for the two non-synthetic Purolator oil filters, the PureOne and the Classic. Now why would that be? Could it be because the PAPER filters would break-down and begin to deteriorate after that interval? Yes, the paper used in oil filters is specially treated, but it is still not as long lasting as a synthetic medium.

As of June 2012 the NAPA part number for the MagneFine filter is a transmission p/n 1-8514 or p/n 1-8515, cost of $24, with the 3/8-inch hose-ends. I have purchased two filters, each with one of the two different parts numbers just listed. The filters appear to be the same, and I do not know why the two different part numbers.

The box says NAPA, the filter label says Raybestos/ MagnaFine. Yes, I am using the exact same filter in both the Power Steering and Transmission fluid lines. The same MagneFine is specifically designed to be used in both applications.

Last edited by dcmodels; 01-14-2013 at 01:14 AM.
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Old 03-16-2013, 01:30 PM   #8
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Like the idea. Not sure if I'm ready for this one.
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