Pilot34119

2005 Honda Pilot leaks coolant into the ATF passing through the radiator resulting in a ruined transmission.


How prevalent is this issue. The car is new to me and has 59K miles on it. Should I have the radiator replaced as a preventative measure or is the concern on other sites overblown?

speedlever

Sounds like the SMOD (strawberry milkshake of death) issue. Seems to be fairly common with Honda and other makes as well that use the same design radiator. There are only about 1/8th inch of threads that hold the heat exchanger in the radiator. The new Denso radiator available from Rock Auto appears to have a new design which hopefully eliminates this issue.

From what I've read, once that fitting fails and coolant mixes with tranny fluid, your only hope of saving the tranny is to immediately shut down and not try to nurse it along until you find a convenient stopping point.

I'll edit this this shortly and post a link to a thread that may be of interest to you.

Edit: 59k miles is very low for a 12 year old vehicle.

This thread comes from a Ridgeline forum, but the issue is the same. Also has affected the Acura MDX, NIssans, and other makes too.
http://www.ridgelineownersclub.com/f...-fittings.html

Pilot34119

I've decided to get the radiator replaced, you think the new design Denso is good to go? I had the job quoted using a Denso for $508 out the door.

ETA: Whoa, I didn't realize how inexpensive the parts were. That makes me feel a little better about there being enough $$ for the right labor and fluids to be sure things are being done right. The dealership quoted me more than double what this mechanic quoted. The mechanic has a great rating on yelp as well which helps since the car is at our second home and I have no feel for who the good mechanics are down there.

speedlever

The general consensus at the ROC is that the new Denso is good. How to differentiate from the old style, I do not know unless the p/n is sufficient.

Regardless, if you've had the SMOD issue, I'd definitely replace the radiator and flush the tranny (for Honda, that's a drain and fill operation) at least 4 times. It might be worth investing in a fluid analysis at that point if tranny operations seem normal, just to make sure all the coolant is out. Honda does not support any type of tranny flush except the D&F method unless you can find a shop that lets the engine suck in clean fluid from a bladder while the output hose goes into a waste bucket. No power flushes for a Honda auto.

Good luck. I hope you can save your tranny.

And just curious, but how did you find such a low mileage 2005 Pilot?

Pilot34119

We bought a second home in Florida from an older couple who were permanently moving back to Switzerland. They sold us the house "turnkey" / fully furnished since they couldn't take anything with them. The Pilot and a golf cart fell into that "can't take it with you" category and were part of the overall deal. They were the original owners and had the car maintained by the dealer they bought it from. I attached a copy of the service history that I got from the dealer. The car was used during the October - April season in SW Florida.

We are going down to Florida on Friday. Maybe I'll be pleasantly surprised that the transmission was replaced already. As you will see, this car was very well maintained. The transmission isn't mentioned anywhere in the service record, but maybe.......

speedlever

Nice!

Looks like you already have a new TB/WP at 47k miles. Not sure what svc trans indicates. They would typically need about 3.5 qts of tranny fluid to do a drain and fill... done at 27k miles. From the dealer, I expect 4 qts of ATF-Z1 would be more than $15. So maybe the tranny fluid was low and they added a qt or two?

And at 52k miles, looks like they changed over to DW-1 tranny fluid. DW-1 replaced Z1 in 2011, iirc. And they did another tranny fluid D&F at 54k miles and again at 56k miles? It should have at least one more changes (D&F) to get to about 88% DW-1.

I'm surprised to hear that you had a SMOD issue with that vehicle. But it should definitely be worth saving!

IIRC, the 2005 Pilot was the last year that the transfer assembly was lubed by tranny fluid. In 2006 and on, they separated it from the tranny and began using hypoid gear oil for the transfer assembly. Ergo, I'm not sure if the 2005 Pilot has the same tranny fluid capacity as my 2006 Pilot or not. If so, here's a chart to approximate the %age of DW-1 after x amount of fluid drain and fill operations.

Pilot34119

I didn't have a problem, that's what I'm trying to avoid.

I figure $500 for peace of mind is a bargain. I'll check the car first thing when I get down to Florida. Maybe it will show signs of having been replaced already. It sort of surprises me that the previous owner wouldn't have had it done considering the way he maintained the car otherwise.

speedlever

He probably wouldn't have known about it unless he participated in enthusiast sites like Piloteers.org or Ridgelineownersclub.com, etc.

Those who don't frequent those forums generally come to those forums after the fact and bemoan their fate. And justifiably so. You wouldn't expect Honda to have problems like that.

Btw, check your spark plugs for proper torque. Loose plugs have been another one of those commonly rare engine destroyers. (Oxymoron, I know!) As long as none are loose, you should be good. Be careful of overtightening in an aluminum head. 13 lb-ft is the spec for my Pilot and RL spark plugs. But if you hear any unusual ticking sounds, that could be a sign of a loose spark plug.

Fwiw, I proactively replace the radiator when I do the TB/WP service, just to be safe. I'm not aware of anyone who has driven enough to know if a 2nd radiator is needed down the road.

Pilot34119

I finally got a look at my radiator and the connections and the washer between them look clean and show no signs of corrosion. I could only see the one to the left as I looked down from under the hood. The car has always been in Florida and has had no exposure to road salt, etc. Previous owner said he didn't know there was a radiator issue - radiator was not replaced by him.

2x0

You shouldn't have any problem with yours being in Florida, and with low miles. The corrosion is usually attributed to salt on roads, but even up north most people aren't replacing the rad as a preventative measure until 100k miles.

I have a 2006 with 120k miles all in MN and it's still doing fine. The fittings are corroded, I plan on swapping the radiator next year. As long as the fittings don't show signs of bad corrosion, you'll be fine.

speedlever

Part of the confusion is whether the issue is external (environmental) or internal (dissimilar metal corrosion). Not sure if that's been proven one way or another. But I agree there's not likely any cause for concern. Yet.

Pilot34119

This whole problem relates to coolant mixing with ATF. It seems like most of the judgements about the condition of the radiator and the likelihood of a problem is based on the visual inspection of the connection hardware. I must be missing something because in my mind, if the threads fail and the connector pulls out you'll lose ATF, but how does the coolant get into the transmission unless the failure is internal? I think the only way you get coolant into the ATF is if the chamber carrying the ATF through the coolant bath is breeched. What am I missing?

speedlever

The problem area that I mention has to do with the visual inspection. All you can see is the corrosion of the Belleville washer. Whether or not that (corrosion associated with the Belleville washer) causes the internal failure where coolant enters the tranny or whether the fitting fails because of dissimilar metal corrosion, I don't know nor do I know anyone who does. Ergo, a proactive change of radiator at the time of the TB/WP service seems prudent.

2x0

If you do some searching around on piloteers.org there is a good write up on it somewhere.

It is caused from external corrosion of the washers where the trans cooler lines attach to the radiator. The washers will "swell up" once severely corroded, which pulls the threaded part of the radiator out and allows mixing of the fluids on the inside. There is only a thin wall of metal separating the two fluids, so when the outside wall of the radiator detaches from this it allows the mixing. Usually you won't even have any leaking of fluid, just mixing. But the corrosion is caused from external sources.

speedlever

Here's a nice radiator comparison thread (for the Honda Ridgeline) that you may find useful:

Radiator comparison: Denso/Spectra/OSC - Honda Ridgeline Owners Club Forums

speedlever

Not necessarily. Some owners are reporting little actual surface rust but evidence of galvanic corrosion. So I suspect the issue is more complex than simply external corrosion alone. For instance:
Honda Ridgeline Owners Club Forums - View Single Post - Pictures of corroded/rusted radiator fittings
Honda Ridgeline Owners Club Forums - View Single Post - Pictures of corroded/rusted radiator fittings

There's only about 1/8 inch of threads holding the fitting together:

Pilot34119

I had a Denso installed a week or two ago. Hopefully, that should take care of my last worry about my Pilot.

speedlever

As well as that one has been maintained, I certainly agree! Did you have a dealer do the work or an indie Shop? Just curious what it cost to have it done? I estimate a max of 2 to 3 hours work, but the Pilot radiator may take more time than the Ridgeline radiator.

Pilot34119

I went to an independent mechanic and paid $636 out the door for a Denso radiator, upper and lower hoses and the fluids. I don't have the paperwork handy, but I think they marked the radiator up 100% or so.

speedlever

Thanks.