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Discussion Starter · #1 ·
I have a 2008 Pilot that developed a major oil leak about a year ago. It was so bad, if you drove it 30 miles and parked it, it would leak 1/4 quart on the ground, leaving a 16” diameter puddle on the ground. I have spare vehicles, so I parked this Pilot on the car lift in May and have worked on it in my spare time.

In August, I climbed under it to deep-dive the issue. It appeared to be leaking from the rear main seal. I spent 30 hours dropping the K-member, pulling the transmission, changing the rear main seal and resealing the oil pan. Put it all back together feeling pretty good about myself. Fired it up and took it for a test drive, and it leaked as bad as it did before I started working on it.

Super frustrated, I parked it back on the lift right away, and let it sit until December. I bought some UV dye and a flashlight, and drove it one mile. Put it back on the lift, and it had oil all over the drivers side of the engine. At that time, I had thought that maybe something else was leaking, because the rear main seal was a pretty straight forward fix. Tried to think of what else it could be, possibly something in the valley between the heads? Was so mad, I let it sit again until this March.

I forgot about the possibility of a leak in the valley, so I bought a new rear main seal and a redi-sleeve for the crank. I took it all back apart, and redi-sleeved the crank, and put in a new seal again. I bolted the trans back in, and started to put the 8 torque converter bolts in. Just by turning the crank by hand, the oil came streaming down behind the flywheel. I stopped, and pulled the transmission out again. The oil is leaking from the hole above the rear main seal plate, which appears to be in the valley between the heads. So, this whole time, THE LEAK IS AT THE TOP OF THE ENGINE!!

It hasn’t cost me much money, just 50+ hours of time to figure out where it’s coming from. Now, after the whole back story, what could be leaking in the valley between the heads? The truck has 221k on it, and I changed the head gaskets at 208k due to coolant consumption. Could it be head gaskets, or is there something else in the valley? I hate this Pilot. I feel all I’ve ever done is work on it. I just want to fix it because I don’t want it to beat me.
The question have is, the engine is hanging in the engine bay by a motor mount and the engine support bar on the top. I’m probably 1-2 hours away from just dropping the engine. Should I button it back up and start working on the top end, or just pull it, put it on an engine stand, take it down to a short block, and just reseal the whole engine. And the main question, any idea what would be leaking in the valley?

You can see the 1/2” hole above the rear main plate in the picture. That’s where it’s streaming from.

Thanks for reading thru, and I look forward to your responses.
Scott
Engine Auto part Machine Automotive engine part Space
 

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Discussion Starter · #3 ·
There is an oring under the cover that the rear main seal goes in. You have to pull the cover to access the oring. When this oring goes bad it cause the leak you are describing.

View attachment 135018
Thank you sir for your input! I actually replaced that the first time along with Hondabond on the cover and oil pan. Do you have any other ideas? Thanks again for your reply!
 

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2020 Honda Passport Touring AWD Metallic Steel
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Not a common problem so it often gets overlooked, Have you investigated either a head gasket oil leak or some other issue with the the heads?
 

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Discussion Starter · #5 ·
Not a common problem so it often gets overlooked, Have you investigated either a head gasket oil leak or some other issue with the the heads?
If there’s nothing else in the valley, that would have to be what it is. I did the head gaskets about 14k ago, so I wouldn’t know how they would be the issue. Thanks for the reply!
 

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Do you know why this hole is there or what it's for. Is it threaded?
 

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This is definitely a tough one. I think what I would do is pull the upper intake to get a better look at the valley area. It is easy to do.

Does it leak at idle or does it have to get up to 3000 rpm or so to leak? If it leaks at idle and you still can't see anything obvious you could hook up a preoiler setup like you would use on a fresh rebuild. This would let you pressurize the oil system without having to run the car. I have never done it on a J35 but on other engines we would just hook up to the oil pressure sending unit port. I would use a thinner weight oil than you normally use so it will be easier to flow through the system. Of course you could use the oil in the sump. Just remember to adjust the oil level once you are finished.

There are a lot of ideas online for building a preoiler. I know some people who have used the PVC ones with good results. Kinda depends on what you have to work with. Since there is already oil in the system it probably will not take much volume. You could also add some dye to the oil in the preoiler if you have a blacklight.
 

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Check the valley for oil. We bought a 2006 EX 4WD new in 2006 and noticed an oil leak after a week or two. Dealer replaced front main seal (trans end of engine) and still had the leak. Returned to dealer, they noticed the valley was full of oil. Turned out to be porosity in the block casting (really was a poor or not done casting impregnation (which is pretty standard stuff for high pressure die cast block castings) that was leaking oil into the valley. Not sure what the leak rate was, but it filled up the valley in a week or two and then started running over onto the front main that tricked the dealer into thinking that was the leak source. Honda had a TSB for earlier years J35s - The repair would have been Bondo in the leak locations from the outside - no thank you for a new vehicle. We utilized the lemon law provision and swapped it for another 2006 that we still have at 250k miles.
 
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