Engine oil change comments:

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Old 08-02-2010, 12:45 AM
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Engine oil change comments:

My thoughts and opinions (JMOs) about my own RDX oil change(s). This will probably seem a bit ‘wordy’, but some may find the ideas useful and interesting.


OIL CAPACITY of the RDX:
Is anyone else aware that the oil capacity of the RDX engine is 6 quarts, rather than 5 quarts? The service manual states that the engine overhaul oil capacity is 6 quarts, while the drain-and-fill capacity is 5 quarts. So an oil change leaves 17% dirty oil in the engine.


READING the OIL DIP STICK of the RDX:
You can get a reasonable reading of oil level if you let the car sit for at least 5 minutes, after running. The oil needs to drain out of the head back into the pan. Otherwise you will get low reading, and overfill the engine. But …

I get a consistent oil reading only after letting the RDX sit overnight (before starting the engine). The best reading is the first one, since there is no oil in the dip-stick _tube_, and the level on the ‘stick’ is very clear. If I take a second reading, even after wiping/ cleaning the dip-stick, there is some oil along the dip-stick from the oil in the tube from removing the dip-stick the first time.

I have been using Mobil M-110 oil filters. After an oil change, I find that about 6 ounces more than 5 quarts is required to get a ‘full’ reading on the dip-stick. Run the engine after the oil change, then check the oil level the next day.

So how do you tell exactly how much oil to add, when checking after an oil change? Well, the distance between the centers of the two ‘reading-holes’ on the dip stick is 22/32 inches. Sorry, I only do inches, and will let you do the conversions to metric if so inclined.

That means that each 1/32 inch distance on the dip stick is 32 ounces / 22 = 1.45 or 1.5 ounces. That is, a quart = 32 ounces. And the distance between the two reading holes on the dip stick represents 1 quart. Therefore 1/32 inch = 1.5 ounces. Hope this is clear.

So, you take a reading on the dip stick, use your steel rule and measure how many 1/32 inch increments the oil is low (below the top hole on the stick). Say it is 3/32 inches low after an oil change. Then that means you need to add 4.5 ounces = 1.5 ounces x 3 units. A quart bottle of most oil containers is marked in ounces (as well as metric liters).


DRAIN PLUG TORQUE SPECIFICATION:
I feel that the Acura torque specification of 29 ft/lbs is too high, and eventually the pan threads will wear and strip. I have read online, about other brands of vehicles (and some Hondas) having this problem after extended service. The RDX uses a steel drain plug screwed into an aluminum pan.

My observation is that most engine oil drain plugs over the years have had a torque specification of 20 ft-lbs, more-or-less. And the torque spec is the same whether cars or bikes (motorcycles), steel or aluminum pan (threads).

On my RDX I use a copper (not aluminum) washer, and torque to 19 ft-lbs (225 inch-lbs). The copper washer is softer than aluminum, and crushes/ seals at a lower torque. Various size copper (and plastic) sealing drain plug washers are available from your local aftermarket parts store. I bought 14mm copper washers at PepBoys, made by Dorman.

In fact, I use a copper washer and torque of 19 ft-lbs on all drain and fill plugs on my RDX: engine pan, transmission, transfer case, and rear differential. Those applications all use a steel plug into aluminum pan threads.

I guess you could also use a plastic washer on the RDX (well, really they are nylon). Copper washers in the correct size(s) were easier for me to find. My Chevy Blazer uses plastic sealing washers on the front aluminum differential. The drain plug is 12mm x 1.5mm threads, and the torque specification is 19 ft-lbs. It has not fallen out in 100K miles.

Multiply Ft-lbs by 1.356 to get Nm


WHAT IS THE PURPOSE of HELI-COIL ?
The heli-coil is a coil of stainless steel threads, inserted (screwed) into the bolt hole. The bolt threads then bear against the steel threads of the heli-coil, not threads in the actual part. Generally a heli-coiled hole will allow the bolt to break (from tightening), before the (heli-coil) threads in the hole are damaged, even when the heli-coil is installed into aluminum. On my motorcycles I have often installed heli-coils into brand-new aluminum bolt-holes as a preventative measure. It is then almost impossible to over tighten and damage the threads in the hole.

Too bad Acura did not heli-coil the RDX.

My 1998 Chevy Blazer drain plug hole is factory heli-coiled. The torque specification is 18 ft-lbs. This is for a steel plug into an aluminum oil pan. I have watched a 300 pound ‘mechanic’ at Jiffy-Lube use his full upper body strength to tighten the Blazer plug (before I could stop him). I had to use a 1/2 inch drive 14-inch-long breaker bar to remove it myself when I did the next oil change. Yet there was no damage to the threads in the oil pan. Actually, the plug was not damaged either, which did surprise me. The Blazer plug is 12 x 1.75mm. The RDX engine drain plug is 14 x 1.5mm


DRAIN PLUG WASHERS:
The basic ‘problem’ is that the RDX uses an aluminum drain plug washer, which requires a high torque to properly crush and seal. My 1998 Chevy uses a rubber washer, which will seal at “finger-tight”, because the oil in the pan is not under pressure. The required Blazer torque of 18 ft-lbs, is just to prevent the bolt/ plug from loosening.

The Blazer oil pan is aluminum, just like the RDX. Use of a different material washer on the RDX should not be a problem. Other vehicles use washers made of rubber, plastic, fiber, copper, etc. without the plugs falling out.

As for using copper rather than aluminum gaskets (crush-washer), just keep in mind that the washers used in most brake systems are copper (not aluminum). Brake caliper banjo-bolt washers sustain much higher pressures than the engine oil case oil pressure. These bolts do not loosen or leak in use.


WHAT IS WRONG WITH ALUMINUM CRUSH WASHERS ?
Aluminum requires too much torque to crush and seal. But the real problem with aluminum is that when it is dry, it will gall when the plug is screwed into the pan. Galling means that the aluminum washer begins to ‘cold-weld’ or stick to the aluminum pan. The steel plug is ‘slick’ enough, and hard enough, that generally the washer will not gall to the plug sealing surface.

Try WikiPedia for more info on galling. Next time you do an oil change, have a really close look at the used washer. You may be wondering why there are ‘scratches’ or marks on the washer, since the plug and case surface are smooth (at least they were when new). Those marks on the washer are a result of galling.

This galling prevents a smooth torque-down, as the washer sticks and then ‘slides’. I have found it almost impossible to get a valid torque reading with a dry washer and plug. And of course, the friction between the dry components will cause the specified torque reading to be reached at a much lower actual turning force. In other words, the difference between the actual torque, and the reading on your torque wrench, can be 20-50% depending upon whether the components are dry or oiled.

So I am guessing that since Honda assembles their engines dry, then adds oil, that the specified torques give the ‘correct tightness’ when automatic powered torque wrenches are used with dry components on an assembly line. In other words, since the parts are assembled dry, the actual torque of the bolts is much less than the reading on the wrenches used. Actually, the air powered wrenches used will auto-release at the selected torque. The wrenches _cannot_ over tighten the bolts. What? You have never seen air powered assembly wrenches on an actual car line?

Now, you may be thinking that it is not possible to put that oil pan plug back in and torque it ‘dry’. Maybe. But if you walk away for half an hour to let the pan drain, and then wipe off the plug and pan drain-hole, and use a new dry washer, there is really no telling just what torque reading you are going to get.

So why does Honda/ Acura use aluminum washers? No idea. I can only observe that other cars which use copper or plastic (or fiber) washers do not seem to have problems with the drain plugs falling out.


GETTING A CONSISTENT and VALID TORQUE READING:
The only way to get a consistent _valid_ torque reading, is to make certain that the drain plug and washer are lubed with engine oil. And then smoothly (but not too quickly) pull down with your torque wrench. Yes, even pulling down to the required torque too quickly (or slowly) will give a false reading. Also, pulling down to the final reading, starting too close to the final reading, will give an invalid torque. This is because some torque is required to begin moving a bolt which is already partly tightened.

You can practice on your wheel lug-nuts. But do _not_ put any lube on the wheel nuts. They must be dry and clean to use the torque specification for wheel nuts, as stated in your owners manual. Ever wonder why there are steel inserts in the wheel holes for the studs? That is so that the steel wheel nut bears on the steel insert in the wheel. Steel-to-steel instead of steel (nut) to aluminum (wheel) hole. That reduces the galling. And that is why the wheel insert and nut should be dry and CLEAN.

The problems of galling, notchy movement, etc. are less with plastic or copper washers. These materials are smoother and ‘slicker’ than aluminum. Still, when torquing drain plugs, I just put a smear of oil on the plug and washer surfaces, no matter which material is used. Then I torque using about two movements to final torque.

Have you been wondering why the force required to remove those drain plugs seems so high? You may be thinking that the plugs were over-torqued at the factory. No, it is because the aluminum washer has cold-welded to both the case/ pan and the plug. That loud ‘pop’ when the plug finally breaks loose, is the washer releasing. This is less of a problem when the plug (and washer) was lubed with oil during installation. You will especially want to lube the transmission washer/ fill plug, since otherwise there is no reason there would be any oil on them.


USE A TORQUE WRENCH RATCHET ADAPTOR:
Use an adaptor between the torque wrench and the socket on the drain bolt. A torque wrench has no ratchet feature. The adaptor that I use _is_ a ratchet, with a female 3/8 inch drive on one side, and a male 3/8 inch drive on the other end. This is extremely useful when the swing area for the torque wrench is limited (which is always the case for me when laying under my car on the garage floor).


WHY SAFETY WIRE A DRAIN PLUG ?
The RDX drain plug provides no structural support. It just holds the oil in the case, under no pressure. So a lower than specified torque can be used, to prevent wear of the aluminum threads. Safety wire can be used to ensure that the plug cannot fall out.

Safety wiring a drain plug (or other fastener) will ensure that it cannot loosen from vibration and heat cycling, etc. Generally any fastener, whether bolt or nut, should be properly torqued even when safety wired. Proper torque is required for the fastener to correctly hold the parts together. The safety wire is a backup, to prevent loosening. Just remember that a drain plug is not holding any other parts together, so a lower than specified torque is no problem, so long as it does not fall out (and dump your oil).


HOW to SAFETY WIRE:
There are three basic sizes of safety wire in use. But for general use, drill holes of 1/16 (0.062) inch in the bolts, and use 0.032 inch diameter wire. Here is a nice pdf publication on fasteners in general, with a section (7) on safety wiring. Sorry if this violates any forum rules about posting links.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2007.pdf

I will not describe here how to do safety wiring. The required information can be found online. Wiring is straight-forward, but does require some basic skill to drill the bolt and do the wiring. I have been doing this to various motorcycle bolts/ nuts for 40 years. You do not want any bolts falling off when you are 30 miles into the Mohave Desert and the temp is over 100 degrees.

If you are concerned about whether or not you can do safety wiring, just buy a spare drain plug and give it a try. Even if you try drilling the original plug during an oil change, the way that the plug is to be drilled will not render the plug useless even if you mess up on the drilling. I have damaged more than one bolt or nut in my life. Just put it back on, and go buy another one to drill. The usual problem is breaking a drill bit in the bolt/ nut. Just pull out the remainder of the drill bit with pliers – the bolt can still be used.

Aluminum Honda/ Acura magnetic drain plugs are available. Aluminum is much easier to drill than steel. Also, aftermarket drain plugs are available that are already drilled. All Honda late model drain plugs are the same size, and will fit most Acura models. Again, the size is 14 x 1.5mm. Search online.


WHICH TYPE of DRILL BIT for SAFETY WIRE ?
My suggestion is to use a titanium 1/16 inch bit. I have used the regular high speed steel (black) bits, but when I do, I use a NEW bit for each new hole. A titanium bit can be used to drill up to 3 or 4 holes, so the higher cost is not really higher. And the titanium bit will drill faster. It will dull less because it can take the high heat of drilling a hardened steel bolt. The bit is ‘done’ when the gold on the face of the cutting tip has worn off.

If you have a fixture for the bolt and a drill press, use a cobalt bit. It will cut through the bolt like butter. But the slightest slip or offset will shatter the bit like glass. I drill my holes by holding the bolt and drill by hand (or a vise). So I use titanium drill bits.

Finally, you may be thinking it is impossible to drill a straight hole through the head of a bolt. Well, almost. Besides, it is only required that you drill more-or-less from one flat to the opposite flat of the bolt head. Perfect is simply not required.


WHERE TO BUY SAFETY WIRE:
Safety wire can be purchased at various places. My local motorcycle parts store has 25 feet of 0.032 inch wire for $8. Various car/ motorcycle/ cart racing parts houses (brick or online), sell one pound spools for less than $20, which is over 300 feet.

I purchased a one pound spool of 304 soft stainless steel wire 0.033 inch, from a local tool supplier for around $18. You will need about 2-feet of wire for each bolt, not matter how close it is from the bolt to the fixture hole. This is because you need several inches on each end of the wire to hold with your hands. I have personally never used one of the specialty safety wiring (twist) pliers.

JMOs
Old 08-02-2010, 12:48 AM
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Good info!
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