F'n Rear Main Seal!

[RobertK]

Ok, this is the second time this has happened.

After about a week of breaking in the engine we just rebuilt we decided to use 0w-30 Castrol Synthetic for break in. The plan is a use it until the end of June and start running RP 20W-50.

After the problems we had with my new rear main seal we made sure to be very thorough in replacing it on his car. Well guess what? Today we do a random check and the fuckin rear main seal is starting to leak and is getting splattered on his tranny and undercarriage.

WTF? Does it take special mechanical powers to install these damn things?

I can only hope that the problem is because he's using 0W-30 and it clears up when he switches to 20W-50 but something tells me it's gonna leak either way.

[jlevie]

While 0w30 is really too light for where you are at this time of year, a bad seal isn't going to stop leaking with the heavier oil that should be in the car. The leak could be from the rear main seal or the transmission input seal. It will be obvious once the transmission is out.

You want to take a critical look at the at where the rotating parts contact the seal. grooves or a rough surface will prevent the seal from working. And when installing a seal it is very important that it be driven in squarely with pressure applied only to the outer edge of the seal.

[Adrian_Visser]

im no expert on rear main seals but ive heard that some synthetic oils can screw up seals and gaskets in cars that werent originally designed to use synthetics

[PiercedE30]

that's usually only the case when the motor has been run for a while with dino oil, and that wouldn't mess with a seal that has been recently replaced, it would be a seal that has worn down and is only not leaking when using dino oil.

[maniacmatt]

I thought you were supposed to break in a motor with conventional oil and then switch to synthetic if you so desired?

[rcko]

You want to take a critical look at the at where the rotating parts contact the seal. grooves or a rough surface will prevent the seal from working.

also ck the mating non rotating surface on the engine block side. Scratches, dirt etc will allow it to leak also. Sometimes using some permatex etc on the non rotating portion helps seal the small imperfections.

Hopefully once you go with the 20W things will get better...

[HST]

I don't remember replacing the input shaft seal. Here in TN, if has been in the 90's if that makes a difference.

[DJB]

im no expert on rear main seals but ive heard that some synthetic oils can screw up seals and gaskets in cars that werent originally designed to use synthetics

That only applied to very old seal formulations. Even the original e30 engine seals are fine with any type of synthetic oil base stock.

A 40+ year old car likely has had the seals replaced. And someone driving a 40+ year old car likely knows exactly how to care for it, so repeating obsolete advice won't help.

My guess is that the leak is on the transmission input seal, or the gasket where the seal carrier meets the block or oil pan.

[RobertK]

Both the input shaft seal and output seals were replaced.. as was the selector shaft seal.

The oil leaking from the bell housing is definitely motor oil. It's tinted brown and stains the driveway. The tranny is full of Royal Purple Syncromax so if it were the transmission it would be much darker.

[nando]

the seal usually wears a groove on the crankshaft after many miles of use. did you make sure to press the seal in a little further, so it would contact a "new" area of the crank?

[RobertK]

the seal usually wears a groove on the crankshaft after many miles of use. did you make sure to press the seal in a little further, so it would contact a "new" area of the crank?

Hell no.. I used some scotch brite pads to smooth out the area and tried to install the new seal in the exact same spot as the old one. I guess that's where I probably fucked up.