ST165 oil leaks from back of the engine

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ST165 oil leaks from back of the engine

Postby Maet » Mon Oct 11, 2021 5:17 pm

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.
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Re: ST165 oil leaks from back of the engine

Postby alltracman78 » Tue Oct 12, 2021 1:19 pm

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.
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Re: ST165 oil leaks from back of the engine

Postby Maet » Fri Oct 15, 2021 5:13 am

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
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Re: ST165 oil leaks from back of the engine

Postby Maet » Sat Oct 16, 2021 10:09 pm

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...
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Re: ST165 oil leaks from back of the engine

Postby abeans » Sat Oct 16, 2021 10:37 pm

If it makes you feel better the MR2 guys have that on the firewall side.
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Re: ST165 oil leaks from back of the engine

Postby Tippo » Sun Oct 17, 2021 8:05 am

abeans wrote:If it makes you feel better the MR2 guys have that on the firewall side.


I know this all too well lol
1992 SW20 MR2 Turbo 4th Gen 3SGTE Swap. Aquamarine Pearl. Project "Prissy"
1992 ST185 Celica All-Trac Turbo. Teal Metallic. Project "Lazarus"
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Re: ST165 oil leaks from back of the engine

Postby rallygarage » Mon Oct 18, 2021 11:04 am

Oil seal inside destriburor? Not the o ring on the outside.
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Re: ST165 oil leaks from back of the engine

Postby Maet » Mon Oct 18, 2021 3:57 pm

rallygarage wrote:Oil seal inside destriburor? Not the o ring on the outside.


Nope, I said I already did the distributor O-Ring, but it's the top bolt for the oil cooler that's just constantly leaking as soon as the engine starts. Does the MR2 use a heat exchanger style oil cooler instead of the ST165s coolant box thing?
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Re: ST165 oil leaks from back of the engine

Postby alltracman78 » Mon Oct 18, 2021 4:50 pm

No, all the 3SGTEs use the same type. They're not all identical though.

Not the end of the world.

Remove your alternator, remove and carefully hang your ac compressor and use patience. Make sure you replace all the seals and hoses in there while you're at it.

Considering how old the engine is might be time to pull it and reseal everything?
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Re: ST165 oil leaks from back of the engine

Postby Maet » Mon Oct 18, 2021 5:13 pm

alltracman78 wrote:No, all the 3SGTEs use the same type. They're not all identical though.

Not the end of the world.

Remove your alternator, remove and carefully hang your ac compressor and use patience. Make sure you replace all the seals and hoses in there while you're at it.

Considering how old the engine is might be time to pull it and reseal everything?



Already pulled it twice for clutch stuff and put all new gaskets on everything, along with most hoses and lines. I pulled the engine again after my slave cylinder ate my throwout bearing and did the valve stems while I was there. Bold of you to assume I still have AC, I was planning on removing the entire turbo assembly by disconnecting the 4 bolts that hold it to the exhaust manifold but I'll give it a shot with just the alternator.
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