Rear main seal replacement

GuyLedouche · 10-30-2022, 05:13 PM

My 2015 has less than 30k miles and has been oozing from the bellhousing for a while now. Each track day it gets worse. It seems early for the seal to fail. Has anyone had the same problem?

If I'm going to be in there is there a 6MT clutch upgrade I should consider? Mostly a track focused car at this point.

JAI///M3 · 10-31-2022, 03:13 PM

In general, a few things come to mind with rear main seal leak/failure.

1. High crankcase pressure. How's you're PCV system health? Are you pushing high boost? High mileage/ high blow by?

2. Engine oil level? Are you running higher level than recommended? Do you trust your level sensor? This would be bad for other reasons as well.

3. Trans input shaft/ clutch condition? Heavy duty clutch installed? Flywheel in good shape?

I realize these are all more questions and zero answers, but this is what I would be working through.

GuyLedouche · 10-31-2022, 07:18 PM

No pcv noise. I have a catch can that hardly collects any oil. I run BM3 stage 2 on stock turbos.

I just started runner the bimmerworld gt4 oil kit. It was weeping long before that.

Stock clutch less than 30k miles on the car.

JAI///M3 · 11-01-2022, 08:22 PM

Does seem odd but I suppose if it's 30k miles worth of track time it isn't too bad.

Any chance it's the valve cover leaking from the rear and dripping down?

GuyLedouche · 11-10-2022, 12:31 PM

I don't have PCV squeal but when I pulled the oil cap off a good amount of pressure was released. Guess I found the culprit. Thanks for the comments.

JAI///M3 · 11-10-2022, 12:35 PM

In other platforms I've seen these types of minor real main seal leaks resolve themselves once crankcase pressure (or lack thereof) has been restored with proper ventilation.

Hopefully this is the case for you!

GuyLedouche · 11-10-2022, 01:21 PM

Quote:

Originally Posted by JAI///M3

In other platforms I've seen these types of minor real main seal leaks resolve themselves once crankcase pressure (or lack thereof) has been restored with proper ventilation.

Hopefully this is the case for you!

I'll just replace it this winter. I try to be proactive with maintenance, probably because I'm a pilot haha.

andrei.m4 · 11-14-2022, 02:42 PM

I replaced it! At 100k km. After that at 140k km valve cover failed also.

10-30-2022, 05:13 PM	#1
GuyLedouche Lieutenant 588 Rep 467 Posts Drives: F82/718 GT4 Join Date: Nov 2018 Location: NH iTrader: (2)	Rear main seal replacement My 2015 has less than 30k miles and has been oozing from the bellhousing for a while now. Each track day it gets worse. It seems early for the seal to fail. Has anyone had the same problem? If I'm going to be in there is there a 6MT clutch upgrade I should consider? Mostly a track focused car at this point.
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10-31-2022, 03:13 PM	#2
JAI///M3 Lieutenant 528 Rep 502 Posts Drives: F80 M3 Join Date: Dec 2021 Location: East Bay iTrader: (0) Garage List 2018 F80 [0.00]	In general, a few things come to mind with rear main seal leak/failure. 1. High crankcase pressure. How's you're PCV system health? Are you pushing high boost? High mileage/ high blow by? 2. Engine oil level? Are you running higher level than recommended? Do you trust your level sensor? This would be bad for other reasons as well. 3. Trans input shaft/ clutch condition? Heavy duty clutch installed? Flywheel in good shape? I realize these are all more questions and zero answers, but this is what I would be working through.
	Appreciate 2 TractionControlDelete4588.50 GuyLedouche587.50 Quote

10-31-2022, 07:18 PM	#3
GuyLedouche Lieutenant 588 Rep 467 Posts Drives: F82/718 GT4 Join Date: Nov 2018 Location: NH iTrader: (2)	Rear main seal replacement No pcv noise. I have a catch can that hardly collects any oil. I run BM3 stage 2 on stock turbos. I just started runner the bimmerworld gt4 oil kit. It was weeping long before that. Stock clutch less than 30k miles on the car.
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11-01-2022, 08:22 PM	#4
JAI///M3 Lieutenant 528 Rep 502 Posts Drives: F80 M3 Join Date: Dec 2021 Location: East Bay iTrader: (0) Garage List 2018 F80 [0.00]	Does seem odd but I suppose if it's 30k miles worth of track time it isn't too bad. Any chance it's the valve cover leaking from the rear and dripping down?
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11-10-2022, 12:31 PM	#5
GuyLedouche Lieutenant 588 Rep 467 Posts Drives: F82/718 GT4 Join Date: Nov 2018 Location: NH iTrader: (2)	I don't have PCV squeal but when I pulled the oil cap off a good amount of pressure was released. Guess I found the culprit. Thanks for the comments.
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11-10-2022, 12:35 PM	#6
JAI///M3 Lieutenant 528 Rep 502 Posts Drives: F80 M3 Join Date: Dec 2021 Location: East Bay iTrader: (0) Garage List 2018 F80 [0.00]	In other platforms I've seen these types of minor real main seal leaks resolve themselves once crankcase pressure (or lack thereof) has been restored with proper ventilation. Hopefully this is the case for you!
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11-14-2022, 02:42 PM	#8
andrei.m4 Second Lieutenant 113 Rep 291 Posts Drives: bmw f82 Join Date: Mar 2019 Location: Romania iTrader: (0)	I replaced it! At 100k km. After that at 140k km valve cover failed also.
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