Page updated on 04-24-2018

Pilot Transmission Radiator problem

08-11-2011, 01:50 PM
2005 honda pilot exl 76,000 miles
Problem: Transmission and Radiator fluid mixing.

So, I've noticed a coolant smell for quite a while now, but never saw a leak. Finally, I took it to the shop and got it checked out. They claimed they didn't smell anything (although I still could). They put a pressure test on it and said it came out clean. At that point, I gave the dealer the benefit of the doubt and went back home. fast forward 3 weeks and the you know what hit the fan. I noticed a strawberry colored milky substance leaking out of my coolant resevoir. Turns out, that my worst nightmare came true and the transmission cooler failed allowing transmission fluid and radiator fluid to mix. Again, I took it to the dealer who told me that I needed to replace the transmission and the radiator. They quoted me 5,100 dollars to fix it. Needless to say, I am totally outraged. Mainly because this is something that could have been prevented. Regardless, I would love to hear from others that may have had this problem and warn others that this could happen to them. I looked this up on the internet and found about 3 other people who had the same thing happen at about the same mileage. The dealer said he has seen it before in a Ridgeline, but I think it is more prevalent that he is telling me. I called a Transmission place and they told me that they have seen it before in Hondas. I'm wondering if there will be an eventual recall. Anyway, any advice would be much appreciated. At this point, I am pressing the dealer to give me some sort of Honda Goodwill reimbursement. I will update if there is any progress.


08-11-2011, 02:26 PM
The transmission fluid is usually running through a tube in the bottom of the radiator to cool the transmission fluid. It sounds like this tube has a leak.

I don't think you need a $5,100 repair bill, just some diagnostic work to see where the leak started. Try and climb higher up at your dealership, if you don't get the answer you need, go above them.Usually the district parts and or service manager can make decisions like this.

If not covering the repair in full some sort of discounted labour rate should be negotiated. Get this in writting before committing to the service work.

08-22-2011, 09:08 PM
This weekend my 2005 Pilot ExL encountered this same problem. No smells or leaks until fluid/coolant was pouring out of overflow bottle.

My indep honda specialist told me that they have run into this 3 times in the last year on two pilots and one MDX. He's replacing radiator and thermostat and flushing transmission a few times. Total closer to $1500

Any feedback would be helpful

08-31-2011, 10:39 AM
A tricky question here is how to spot the leak before big troubles begin.

Can anybody come up with the solution other than checking coolant and transmission every day?


09-02-2011, 02:01 AM
If anti-freeze entered transmission,,,,,,it will fail,,,guaranteed,,,,the coolant destroys clutch linings,,,,quite quickly!!! replacing internal cooler with external cooler as a stand alone cooler is the best way to go...tough to test for this problem other than PM it by replacing it with external type

10-05-2011, 07:19 PM
2005 Pilot with 93,000 miles, transmission started acting up today and after lifting the hood transmission stick is dry and overflow radiator bottle leaking strawberry milk fluid. Seems to be the radiator and trans fluid mixing - has anyone had any luck flushing the trany and replacing the radiator without replacing trany?

10-06-2011, 01:06 AM
you might luck out if the antifreeze didn't contaminate trans too bad,,,,,,replace oil cooler with external unit ,,,drain trans,,,,re-fill and good luck,,,,if trans is somewhat milky,,,,run a bit and re-drain trans...oh yes,,,,flush rad also and plug internal cooler....good luck!!!!!

10-07-2011, 09:10 AM
Thanks for the info, having the work done today, was lucky - there was very little trace of coolant in the transmission. New radiator being installed and flushing both systems ......i will follow up in a few weeks.
great site for information!

10-08-2011, 12:58 AM
I don't think I would go with a radator with an internal cooler especially if it is OEM !!!! An external cooler is the way to go!!!!!

10-08-2011, 09:32 AM
We are having a similar radiator problem with our 2004 MDX. I will post what we find. It pretty much just started to leak profusely out the bottom (strawberry colored stuff describes it well :D), and now it needs more coolant just to move it on the driveway; otherwise it runs (and ran) fine. I will update once we really take a look at it.

11-11-2011, 02:14 PM
We had the same problem with our 2005 Pilot. The radiator failed and the transmission fluid came out through the radiator overflow. We had hoped that we could just replace the radiator and have the two systems flushed. It didn't work. About two weeks later the transmission started to slip. We ended up having it rebuilt. My husband replaced the radiator (about $300 for parts), the system flushings were about $300, and the transmission rebuild was $2,700. It is very disappointing that Honda would have a design flaw that results in a damaged transmission when a relatively inexpensive part fails.

07-13-2014, 08:38 PM
HI People and trannyman
Our Honda Pilot 2005 started smelling bad then as the others on this thread state
Puff of smoke
Temp gauge way up
Pink Brown slime in overflow
Well if I had been wiser and trusted the few bad reports over the good overall msn reports I may not be writing here
I may have blown my chances of saving tranny by nursing it home the last 2-3 miles as Trannyman states that contaminants kill clutch linings Crap
I talked to my mechanic here in -30 winters Canada and although I mentioned the external tranny cooler a brilliant idea my tech says likely not feasible in our climate
Very disappointing in Honda in not separating system to prevent what?, them making 3-5k in tranny work is it engineering piracy or just weak design???
Im checking now if we can put in a external that can heat tranny oil independatly now trannyman and other unfortunate buyers

06-10-2015, 09:07 PM
I've been reading this thread and I'm now very grateful that I had. My wifes 05 pilot has a radiator leak so I will be replacing it. Now that I am aware of this issue I plan on installing an external tranny cooler while I have the radiator out. The only question I have though is that the directions I've seen for installing the cooler puts it inline with the factory cooler. Am I correct in assuming that what I will be doing is actually bypassing the radiator with the coolant lines from the tranny and going directly in and out of the aftermarket cooler. Also I'm thinking I probably shouldn't cap the in and out tranny lines of the new radiator considering it may create possible pressure build up in the sealed tranny cooler portion of the new radiator. How does my logic sound?

Add your comment to this topic!