Rear Main Seal and Boost
#1
Rear Main Seal and Boost
When I rebuilt my engine i had a rear main seal leak. Got to a point where it was a steady stream of oil. After I removed the rear main I noticed that I lipped the seal which caused the issue. After searching the forum there were many posts on the best way to replace the seal. In my case I dropped the upper oil pan, removed the locating dowels and gently worked the seal on a slight angle to reduce the likely hood of it lipping again. Punched the dowels back in and put all back together.
I'm noticing now that I have slight leak but not sure if it is due to the added boost or the amount of oil pressure. Running about 14psi and see around 90psi oil pressure when oil is cool. (revup oil pump on non-revup)
Is it common to have a bit of oil out of the rear main on a boosted Z?
I'm noticing now that I have slight leak but not sure if it is due to the added boost or the amount of oil pressure. Running about 14psi and see around 90psi oil pressure when oil is cool. (revup oil pump on non-revup)
Is it common to have a bit of oil out of the rear main on a boosted Z?
Last edited by MR RIZK; 08-09-2012 at 07:24 AM.
#2
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IMHO it shouldn't leak at all.. After tearing down my last motor with approx 15 k boosted at 10.5# i specifically checked for leakage at the rear main.. It was dry as a bone n that motor had about 80 k on it...
Plus after a while all that oil would start to give u clutch issues street a while no matter how small...
Just makes sense to me!
Plus after a while all that oil would start to give u clutch issues street a while no matter how small...
Just makes sense to me!
#5
str8dum1 - I did use rtv across the seal as I noticed your post quite a while ago instead of the corners like the fsm says. My concern is that it is squishing past the rtv since rtv doesn't really stick to the rubber seal.
phunk - The pcv is drilled out. This goes to catch can then back to intake pipe with inline check valve. Driver side cover goes to atmosphere and both covers are still joined in the middle.
phunk - The pcv is drilled out. This goes to catch can then back to intake pipe with inline check valve. Driver side cover goes to atmosphere and both covers are still joined in the middle.
#6
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About your breather system. The passenger side being attached to the intake makes it pointless during boost. The boost pressure closes the check valve meaning it won't vent to the atmosphere at all. The drivers side rear port is only 1/8" diameter hole inside that large nipple. You have to drill it out to get any venting from that.
So under boost you are only venting out of a 1/8" hole. Not near enough to reduce the boost pressures in the crankcase. The middle cross over ports are the largest ports and when vented to atmosphere provides the best crankcase relief of pressure.
also, oil pressure will not affect those seals. There is no direct oil pressure on the rear main or front main. Oil will splash up on those from motion or crank windage. Crankcase gas pressures are what would force the oil out of those seals.
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#9
To be honest i read through the long a$$ thread about catch cans and crankcase pressure on this forum and the above is what I ended up with. The check valve is a earls -8AN so it has a decent opening.
Does my setup help CC pressure nfi however open to suggestions.
Does my setup help CC pressure nfi however open to suggestions.
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not sure Mr RIzk, if that passenger side vents when under boost then it should flow enough but it would be restricted by the small openings on those ports. If you have abnormally high blow by then they might not be sufficient for your exact engine then.
are you using the oem nissan rear main seal? The aftermarket ones are junk.
are you using the oem nissan rear main seal? The aftermarket ones are junk.
#15
@binder
Yep new oem rear main and new oem half moon seal. Not sure if related the only other difference between most builds i have seen in the US and mine is that the piston to bore clearance is tighter on mine. Most owners I have seen use about 0.035 where mine is 0.028.
Yep new oem rear main and new oem half moon seal. Not sure if related the only other difference between most builds i have seen in the US and mine is that the piston to bore clearance is tighter on mine. Most owners I have seen use about 0.035 where mine is 0.028.
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Hmm, less clearance I would assume should reduce blow by if it causes any effects. I don't think it would be significant though since the rings will be doing the sealing moreso than the piston walls themselves.
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It should help a lot with crankcase venting. The unfortunate thing is if that rear seal has already been compromised then it might be damaged and continue to leak no matter what.
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I just got my new motor in and started driving it last night to break it in. Sure enough, my mother ****ing rear main seal is leaking. I wish I would have known that was a common problem, I would have been more careful putting in the new seal. Now I have to go and pull the ****ing motor back out again. FML.