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2005 Honda Pilot Leaking Near Radiator

Hello All! Our 2005 Honda Pilot is at it again, causing problems. It is a Wisconsin car and has 150k miles on it. During a routine oil change and tire rotation in the driveway, we found the plastic cowling under the radiator area is wet. It appears to be oil and there are steel lines with rubber tubing on them at the bottom of the radiator that are wet, too. What looks like the bottom radiator support, made of steel, is wet and it appears to be oil. It is difficult to make sense of this area because visibility from my vantage point is poor (I am relegated to laying on the driveway with the car on jack stands).

Before I get started on things, I was doing some research with no luck yet. After the help on this forum for our 1997 Chevy truck I figured this would be a great place for some questions. My questions are:

*Are there typical modes of failure in this area or cooling system on this vehicle?
*Is this likely transmission fluid or is there an engine oil cooler that comes stock on these vehicles?
*Do the steel lines rust or fatigue?
*Is it likely just a hose?

Any help or ideas are appreciated!!

Part Throttle

The first thing I’d do is check fluid transmission fluid and engine oil levels. If the leak has been there for a while, one or the other should be low. This assumes you haven’t changed either for a while. Check any rubber hoses for elasticity by squeezing them. Check for cracks in the rubber, too.

It’s very likely that the transmission cooler line connection on the radiator is leaking and ready to fail completely. This was a somewhat frequent occurrence with the Honda Pilot and related cars in those years (one of them being my 2005 Acura MDX). I suggest making sure the transmission fluid is at the correct level and getting this car in for service as soon as possible.

There’s usually two connections at the bottom of the radiator for the automatic transmission fluid cooler tubing. It’s sort of hard to believe that nearly boiling hot coolant in the radiator could do a very good job at cooling the transmission fluid, but it actually works well, b/c the transmission fluid is even hotter than the engine coolant. Likely there’s a leak at one of those connections, which is causing the transmission fluid to leak out, and accumulating there under the radiator. As advised above, first priority is to make sure both the engine and transmission fluid are at their proper level; if either of those get low the resulting damage could be very expensive to repair. Hopefully it is just a slow leak, a leaky hose or connection, and that shouldn’t prove to be overly expensive to fix.

Sprayed some carb cleaner in the area and starting to thinknit is the lines. Hard to believe they are rubber with hose clamps. Looks factory, too. Still is kind of cheesey. Will take in tomorrow and update!

Honda uses a rubber timing belt on your engine, too. BTW, was that changed around 105,000 miles? If so, it isn’t due until about 210,000 miles if done on time.

Remember that the trans cooler is at the “cool” side of the radiator…hardly “nearly boiling.”


There were TSBs for both oil and trans fluid leaks for the 2005 Odyssey. The '05s were pretty popular at CarComplaints.

The Honda Pilot is at the mechanic. The steel lines are pinholed and rusted. They will be replaced with bulk steel lines and new hoses. Radiator is OK.

Glad I was under the car and “givin’ 'er the once over”. This could have ended badly!

Makes it seem justified that I still do some things myself.

1 Like

Amen to that!
You’re a practicing proponent of something that many of us promote often… the occasional basic “look-see”. Whenever I work on my vehicle, I always take the time to look over everything within visual range for anything that doesn’t look right. I look for seepage, check connections, squeeze hoses, and just plain look hard. I’ve save myself from a few disasters that way… probably a lot more than I remember.

I recall one incident with an old Toyota pickup. I was doing an oil change and found a crusty green spot on the radiator, just above the lower tank. The truck was high mileage, and I knew that color, so I went straight out and bought a new radiator. After changing it out, I stuck my forefinger straight through that crusty green spot. It was ready to hemorrhage at any moment.

There are so many disasters that could be prevented by simply looking around.