Oil leak / Rear main seal or Pan gasket?

[Ron Earl]

I have a 1986 coupe with an automatic transmission. It leaks one quart of oil every thousand miles. The oil is comming from the weep hole in the flywheel cover, one drop every couple of minutes with the engine running in park. The rear vertical face of the oil pan is also wet. I intend to change the rear main seal but I'm concerned that the leak may be comming from the pan gasket where it mates to the "rear main seal retainer" or possibly the "rear main seal retainer" to engine block gasket, both of which require me to drop the oil pan. Any advice would be greatly appreciated I don't want to do this job twice.

Ron

[Randy G.]

Re: Oil leak / Rear main seal or Pan gasket?

That's a tough one.

With the leak as bad as you say, I would remove the flywheel cover, clean the area around the crank and back of the pan very well with a brake spray cleaner and paper towels and run it on a rack and watch it with a flashlight, being careful to not get my fingers in harms way. Shut it off and see if you can trace the leak. The rear main leak will eventually leak down to the pan, but the pan won't leak up to the seal. Typically if the oil is inside the flywheel cover on the flexplate or the flange side of the crank it's rear main. If the oil runs down the back of the pan first then it's the pan. If this has been ongoing and you've changed seals and gaskets before double check to make sure you don't have a small crack in the pan where it seals near the rear main.

If you have any doubt, I would drop the pan and install a new gasket with plenty of good sealer and in the process I'd drop the rear main and rotate a seal in it. Seals are cheap and easy to install. Since it's that far apart and you've got oil in your hair anyway just do it.

RG

[Chuck R.]

Re: FYI

Hi Ron,

Don't discount the oil pressure sending unit on top of the engine up against the fire wall.

My Foreman's 86 started puking A LOT of oil down the back of the engine and all over the flywheel area of the engine and out the flywheel pan.

It's real obvious if you reach back and feel around the sending unit. Not a ton of fun to change out, but it sure beats a rear main seal.

Maybe this isn't the case with yours, but if your not positive where the oil is coming from, keep this in mind as well.

Chuck

[Randy G.]

Re: FYI

Chuck:

I was thinking about that when I posted last night. Gotta look at the intake manifold gaskets and seal where the heads meet the block in the corners. I've seen leaks in that area, too. The oil creeps all over the place.

RG

[Verle R.]

Re: FYI

Also, do not discount the distributor gasket. It will leak significant oil.

Verle

[Randy G.]

Re: FYI

When I was in high school a hundred years ago or so we had a knucklehead in auto shop who liked to sneak out in the student or faculty parking lot with an oil can and pop the hood of any new car the first day it was driven to school. Being the joker he was, he would squirt oil all over the intake manifold and then a shot or two on the exhaust manifold for the smoke effect. I think he was a little jealous of the new car owners, but we sure got a kick out of watching him do it.