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ST165 oil leaks from back of the engine

PostPosted: Mon Oct 11, 2021 5:17 pm
by Maet
Getting pretty frustrated with my oil leaks... Just did my valve cover, distributor O-ring and oil pan gasket (used a pretty terrible cork gasket and now is just Toyota FIPG) and it still pisses oil through the back of the engine. Does anyone have any ideas where I should check? I replaced all the hoses in the back but its not implausible they are leaking now.

Re: ST165 oil leaks from back of the engine

PostPosted: Tue Oct 12, 2021 1:19 pm
by alltracman78
Have you thoroughly cleaned the back of the engine? So you can see where it's coming from?
That's your first order of business. Then you can track it down.
Here are some possibilities.

It could be the head gasket leaking oil to the outside.
Or you didn't clean the sealing surface on the oil pan and bottom of block correctly so the FIPG couldn't correctly attach to the surfaces.
Or the valve cover gasket isn't seated right. I know on the gen II engines the corners over the cam caps need FIPG also. Does the gen I need it?
Can you tell where on the back it's coming from? The timing belt end has the oil pump, it's possible that's leaking.

I don't think there are any hoses carrying oil anywhere on the engine except for the turbo. What about your power steering lines? Or the pump?

Or, your block has a crack in it?
Unlikely, but trying to cover all the bases.

Re: ST165 oil leaks from back of the engine

PostPosted: Fri Oct 15, 2021 5:13 am
by Maet
Yeah I took it to work and used some Gunk engine degreaser and pressure washed it down so now its sparkly clean. Highly doubt its a cracked block or head gasket, I've had the engine out twice and its passed a compression and leakdown test with flying colors, but I did my oil pan with someone who was a certified Toyota/Mitsubishi technician so I highly doubt that's still leaking. But the Gen 1 head does need the FPIG from Toyota (Which I used, but I think it still leaking, but not as bad. I have a twosrus valve cover bolt set coming in for when I redo it.) It's pretty difficult to check at the moment where exactly it is leaking from, but it seems to be above the transmission onto the exhaust and I'm fairly certain my oil cooler O-Rings are leaking so I'm going to redo those and find some new crush washers that fit the oil cooler bolts. This is definitely engine oil though, I can see it on the dipstick and also see oil pressure gradually drop over a few days before realizing I can't even see oil on the dipstick. I also think maybe the reason it seems difficult to track down is maybe the oil cooler is leaking onto the exhaust and just burning instantly so I can't even tell. I did the small distributor O-Ring as well, does the larger internal one tend to leak also?

Thanks for the help

Re: ST165 oil leaks from back of the engine

PostPosted: Sat Oct 16, 2021 10:09 pm
by Maet
Update; disassembled the crossmembers and exhaust and went to check my bolts for the oil pan and snapped one... But I found where my oil leaks coming from, the oil cooler is trickling down onto the sump, then onto the crossmembers which made it look like the back of the engine was leaking. Now I have to deal with this oil cooler leak which looks super fun...

Re: ST165 oil leaks from back of the engine

PostPosted: Sat Oct 16, 2021 10:37 pm
by abeans
If it makes you feel better the MR2 guys have that on the firewall side.