Last night after parking downtown with my RDX, I noticed tons of ATF all over the ground coming from my car.



So I had a friend pick me up with his trailer. I was able to drive it half way up the trailer until I ran completely out of fluid and it wouldn't go anywhere, luckily he had a wench.



Got it home and up on my lift and found that the transmission cooler fitting on the lower tank of the radiator was broke off.

Looks like the steel washer between the fitting and tank had corroded and pushed the fitting out and stripped the threads. ???



So I began to pull the radiator out.







So... my options are: get a new radiator or get a larger transmission cooler and bypass the radiator.

OEM radiator is just above $300, list price is about $415. Aftermarket ones are around $115-150 (don't want that). I did However find a Denso shipped for $178. Denso might be OEM. I couldn't find a marking or stamp.

I could probably find a larger aftermarket cooler for around $75.

What should I do???

 

Oh, and my 2008 RDX tech has 82K miles on it.

 

Denso IS OEM.

 

I want you're garage. lol.

 

lol thanks. just bought it this summer and the first thing i put in was the lift.

 

Thanks. Think I might just buy this Denso one for $179 and call it done. Might as well replace the thermostat while its open too.

http://www.partsgeek.com/catalog/200.../radiator.html

 

I would rather buy Koyo radiator. Part #: A2916
http://koyorad.com

 

^if denso is the Original Manufacture of Acura Radiators......why go aftermarket??

 

Agreed. Plus the only Koyo radiator I could find is $272.

 

I trust Koyo more than Denso specifically because of a common issue with RDX stock radiator. It can become rusted inside and ATF fluid can get into the common antifreeze line.
There are multiple reports about this issue for RDXs with more than 120k miles.

 

TO OP: was the other cooler line fitting similar to the one shown in your original post? when, if ever, was the anti-freeze first changed in your 2008 RDX?

The corroded trans cooler fitting on the radiator is also a commonly reported problem with the Honda Pilot, over on the Honda forum(s). The usual conclusion there is that this problem is caused by electrolysis between the steel fitting and the aluminum radiator.

That would in my opinion, be caused by poor anti-corrosion ability of the anti-freeze (coolant). And then I would wonder if there are other steel/ aluminum parts in the engine cooling system that is rusty?

Or, does it appear that the corrosion is from the outside of the fitting, rather than the inside of the radiator? I cannot tell from any of your pics, nor any of the Pilot pics I have seen.

I also wonder if there is any external visual indication of a problem with the trans cooler fitting, before the line fitting *disconnects*, that is, is there anything we others can look at to determine if there is an impending problem?

 

The fitting is the same. You're correct on the electrolysis. I believe this was the cause for the corrosion. Its an aluminium fitting with a steel washer between it and the tank. Possibly the thread may have been corroded/weakened by electrolysis and the washer corroded by the elements and also perhaps electrolysis.

I bought this RDX last year with 64k miles on it. It has the honda blue coolant so I can assume that it is original or they serviced it at the dealer. I bet that it is original coolant.


I work at place where we design and build corebuilders and crimpers that assembles radiators. We also do much more than that. But we don't make the machine that assembles the tanks individually.

Here is a tank that was laying next to my desk. I believe this is a ford tank.



This one actually doesn't have a steel washer.

 

wow! it must be awesome to work at a place that deals with radiators and you were handy enough to know what was going on!

good shit!!!
looking forward for solutions to the steel washer problem

 

OK, I will need to check my own fitting as I thought the fitting was also steel, like the washer. Anyway, if the fitting is aluminum, then there should be no electrolysis between the fitting threads and the aluminum radiator - unless the coolant has exhausted its corrosion additives.

I understand that the OEM coolant is supposed to last 10 years, but that seems way too long to me ...

I cannot tell from the pic but that nut on the fitting looks like steel. Is it? If so, that would be just the same as a steel washer. But if the nut is aluminum, that would seem to *solve* any problem of electrolysis.

 

If the fitting itself is really aluminum, then the washer should be the only problem. But if the fitting is not aluminum, then the coolant must be kept fresh, with active corrosion inhibitors, to prevent electrolysis between the fitting threads and the radiator tank. I change the coolant every two years - and yes, I know its supposed to last 10 years.

But if the corrosion of the fitting washer is caused by moisture on the outside of the radiator, promoting electrolysis, then simply coat the washer and surrounding area with silicone grease (aka dielectric grease). That will completely waterproof the area. That is what I have done. I also use silicone grease on my drain plugs to prevent corrosion.

 

I decided to just buy a new radiator. I bought the Denso from the link I provided above. Received it yesterday (less than 24hr shipping) :-) Its all done except for the OEM fluids my buddy ordered for me from carquest.

Should have it complete tonight just in time to drive 70 miles to the Pacers game in Indy.

I have some silicone spray. I may just use it.

 

+1

I do the coolant about every 3 years...and I'm going to check those trans fittings in the morning.

 

Checked the fittings. The washers on both have surface rust, but the fittings are firm and secure. I put high-temp grease on the washers.

From OP's pic; the fitting is sealed with an o-ring and the steel washer only provides a rotation surface for the nut (not a sealing washer).

Am considering pulling the fittings to replace the washers, but not so sure if attempting to remove them would crack the radiator.

Might just order a new rad, as the RDX is up to 130k now.

 

Which is why water gets behind the washer. My thought is that grease will prevent water entering behind the washer into the area external to the sealing O-ring. Of course, if water is already in there and there is rust ...

I surely would not try that. If the washers are rusty, then probably the threads on the fitting are also already corroded.

On other forums, for other model Honda/ Acura people are replacing the radiator as PM at 100K, because the other problem is that the trans cooler tank (inside the radiator) corrodes through, and allows coolant into the transmission, destroying it. I do not think that this problem is actually related directly to the fitting/ washer problem, and assume that probably people with the trans cooler corroding have not replaced the coolant often enough - JMO

 

Based on the OP's pic and my own car, it appears that the fitting (not corroded) is aluminum and the washer (corroded) is steel.

Also, the rad itself appears uncorroded. Still not sure what caused the fitting to fail. It seems strange that the rusty washer would expand enough to strip the threads, rather than just crumble . Maybe old coolant?

At 130k miles -- for trans protection alone -- I'll probably go with a new rad. It will be interesting to cut the old rad open and see how the trans cooler lines held up.

 

I may do this since I have no other use for the radiator.

Since it seems you have no problem with buying a new radiator I would probably try to replace only the washer. if it screws up the threads then just order the radiator. I got the Denso from partsgeek within 24 hours.

-Ryan

 

I will also check to see how hard it is to remove the washer. It may be crimped into the fitting.

 

This exact problem just happened to me, I had to get my car towed home.

What was the verdict? Replace the radiator just to be safe?


In fact, I tried to make sure that the fitting in fact came from that hole and just gently pushed the fitting into the hole, but that seem to have broken a seal and all the coolant just started draining out.... it seem the fitting when threaded in pull the trans fluid heat ex-changer against the plastic part which forma a seal and when i pushed in the fitting it broke that seal?


I also have an 08.. certified used... 105k which is 5k past the powertrain warranty... wth!

 

Yes - the fitting cannot be replaced. And the trans heater/ cooler inside the radiator has been known to rust through.

Yes, lube (coat) the new radiator connector washer with dielectric grease to prevent future corrosion - and let us know which brand/ model of replacement radiator you purchase.

 

Same thing happened to me about 2 years ago, driving, gears started slipping and knew something was wrong. Found safe place to pull over, looked, saw it was tranny fluid and knew not to touch the car anymore (thank god saved a trans rebuild). Had it brought to nearest body shop as I was out of town and cost me $750. (Ripoff but nothing I could do).

 

Did you ever upgrade this to a 2-row pass all aluminum radiator? I know they are difficult to find for the RDX.