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Discussion Starter · #1 ·
I have a 93 supra gte converted to single (s369sxe).
I parked the car the whole winter and replaced a few things, including the old oil catch can. Last week I go to turn it on for the first time and right at idle the turbo is leaking from both sides. I thought the seals were gone bad so I had it rebuilt. Still leaking. I check the return line and it’s perfectly fine. I thought the new oil catch can was bad so I put the old one back on, but it’s still leaking. I bought a bigger oil catch can with 2 filters. Still leaking. At this point I believe is blow by. So i go ahead and run some tests. The leak stopped when I tested the car with the return line disconnected from the sump. I let it drain into an oil pan and the oil drains with no problem, but I checked the return flange at the sump and some pressure was coming out. Is there another pcv somewhere? Or some sensors? Idk maybe I disconnected something that’s causing blow by.
Any idea?
 

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Sounds like oil is backing up into the cartridge due to crankcase pressure as you obviously found out. It's the same issue people have with too small of a drain line.

How do you have the catch can run? Sounds like you have the check valve backwards or something. On both my mustang and rx8 I run a simple $5 breather on the oil filler neck and have no issues with the turbo drain. It's likely a simple fix.
 

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Discussion Starter · #3 ·
Sounds like oil is backing up into the cartridge due to crankcase pressure as you obviously found out.

How do you have the catch can run? Sounds like you have the check valve backwards or something. On both my mustang and rx8 I run a simple $5 breather on the oil filler neck and have no issues with the turbo drain. It's likely a simple fix.
Brother I tried starting it without the oil cap, without the dipstick, with the oil lines completely disconnected from the valve covers. It leaked every damn time. It does seem like oil it’s backing up, but I have no idea how there is still pressure in the crankcase after I opened pretty much everything.
 

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Have you visually confirmed that the drain line is completely free from obstructions?

Also, have you done a compression test? Is there any oil leaking from anywhere else like the FMS/RMS etc?

Does your catch can have suction on it from the turbo intake pipe, or is it just venting to the outside via a small filter?

Is your PCV valve functioning properly?
 

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Brother I tried starting it without the oil cap, without the dipstick, with the oil lines completely disconnected from the valve covers. It leaked every damn time. It does seem like oil it’s backing up, but I have no idea how there is still pressure in the crankcase after I opened pretty much everything.

The leak stopped when I tested the car with the return line disconnected from the sump. I let it drain into an oil pan and the oil drains with no problem, but I checked the return flange at the sump and some pressure was coming out
You said the leak stopped when you ran the car with the drain line disconnected from the sump in the first post. That usually is confirmation that oil is backing up.... u also say you could feel pressure pushing out of the fitting. maybe I read it wrong, but the drain will not flow with pressure pushing oil back to the cartridge...

Can you post pics of the catch can setup?
 

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Discussion Starter · #6 ·
Have you visually confirmed that the drain line is completely free from obstructions?

Also, have you done a compression test? Is there any oil leaking from anywhere else like the FMS/RMS etc?

Does your catch can have suction on it from the turbo intake pipe, or is it just venting to the outside via a small filter?

Is your PCV valve functioning properly?
Yes, I disconnected the return at the flange, let it drain into a pan. I turned the car on and it was draining freely.
Compression test and leak down was done before I parked the car for the winter, and it was around 145psi across all 6, and 10% leak down.
Oil catch can has two small filters.
RMS is new. FMS i have to check.

is the PCV on the valve covers the only pcv? If so, both ports were eliminated and welded custom fittings.
 

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Discussion Starter · #7 ·
You said the leak stopped when you ran the car with the drain line disconnected from the sump in the first post. That usually is confirmation that oil is backing up.... u also say you could feel pressure pushing out of the fitting. maybe I read it wrong, but the drain will not flow with pressure pushing oil back to the cartridge...

Can you post pics of the catch can setup?
That’s what I am thinking. I also tested the car with the lines disconnected from the catch can and that didnt fix it.
What i don’t understand is how there can be pressure when all pressure escapes are open? Am I missing something?

261668
 

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how there can be pressure when all pressure escapes are open?
Really bad case of blow-by? Your comp test doesn’t seem like bad rings, though. Seems like the turbo oil return should still drain with the oil cap open and the valve covers vented to atmosphere even with bad blow by.

This last winter some water froze in a low point of my catch can suction line (I’ve since fixed the issue). The turbo oil couldn’t drain because of the high crankcase pressure, and leaked out the rear of the turbo and burnt. It’s fine now because I quickly realized the problem. Anyway, I said all that to ask if maybe your lines to the valve covers had water in them and was impeding the escape of crankcase gases. Can you feel pressure escaping the valve cover lines when the engine is running?
 

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Discussion Starter · #9 ·
Really bad case of blow-by? Your comp test doesn’t seem like bad rings, though. Seems like the turbo oil return should still drain with the oil cap open and the valve covers vented to atmosphere even with bad blow by.

This last winter some water froze in a low point of my catch can suction line (I’ve since fixed the issue). The turbo oil couldn’t drain because of the high crankcase pressure, and leaked out the rear of the turbo and burnt. It’s fine now because I quickly realized the problem. Anyway, I said all that to ask if maybe your lines to the valve covers had water in them and was impeding the escape of crankcase gases. Can you feel pressure escaping the valve cover lines when the engine is running?
i didnt feel any pressure escaping the valve cover.
 
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