Excessive Crankcase Pressure

[ZCarHuevos]

Hi,

I purchased a 2013 Scion FR-S about 3 months ago.

When I bought the car - the intake and exhaust were both removed, an injector seal was damaged. I believe this was because they were aftermarket and the previous owner wanted to keep/sell them. The rear main seal was so far crooked it would shoot out so much oil I could hardly move the car to my lift.
The seal appeared to be installed improperly. I replaced it, reinstalled the intake, purchased a new Borla exhaust, and put the car back together.

From the first drive, the rear main seal began to leak again. Thinking I made a mistake, I installed another one ensuring the seal was barely more than flush (per 1mm spec). Again, after disassembling it it appeared to have been pushed out. From the beginning, I was concerned about the crankcase pressure. I triple checked my hose piping against the service manual/videos and photos I could find on here. I replaced and tested the PCV valve. Grounded the DI ECU as the original bracket wasn't present

I'm truly stumped - I'm thinking compression issues. I'll be buying a new compression tester on Monday as mine is quite old, however most cylinders tested around 90. I knew that was low, but I didn't realize in these cars thats about half of the minimum.
When I pulled the trans the final time, the bellhousing and small area around the seal was full of oil. What would cause this much oil to accumulate here? I had never seen so much. This time the seal was only slightly pushed out.

Some background info:
The car doesn't smoke at all, not even on start up[*]The seals were both OEM from Toyota
The car runs, drives, and sounds perfectly. I drove it about 300-400 miles
I've had an independent shop for years. This is my first time working on a boxer engine, we mostly do Z's/imports. I'm stumped
Smoke tested from the crankcase breather under the AC compresso to the PCV - no blockages
No water in oil, no shavings before/after the first time I refilled it. A head gasket combustion leak test was also done - negative. Car also doesn't overheat

Does anyone have any idea of what would cause excessive crank pressure? I can't think of anything else that would push the rear main out. The crank itself looks fine, no play either. Surely the car wouldnt run as well as it does with only 90 psi compression tested, correct?

I have some pistons/rods/valve springs etc. ready to order for the rebuild as I'm afraid the rings are shot

Not sure if cross-posting is allowed, but I also posted this in the engine section. Apologies if not

[RZNT4R]

Originally Posted by ZCarHuevos

Hi,


I've had an independent shop for years. This is my first time working on a boxer engine, we mostly do Z's/imports. I'm stumped

The difference between a boxer and a 180 degree V engine is the firing angles, so for everything that doesn't involve degreeing the rotating assembly, it's functionally the same as a V engine, just really flat. If you were blowing out the rear main seal on a VQ35 what would you do?

There is only one place that makes pressure in an NA engine. 90PSI of compression is dreadfully low, so check leakdown.

[KillerBMotorsport]

Was that compression test hot or cold?

Was this car ever boosted?

Also, consider adding leak-down testing... You could have a popped ringland that a compression test may not pick up, but a leak-down definitely will.