Rear Main Seal Leak After Rebuild??? - PeachParts Mercedes-Benz Forum

mbboy · #1 03-14-2009, 07:45 AM

I just finished rebuilding the engine of my 81 380sl: both head gaskets w/ head bolt inserts, valve guides, timing chain, upper and lower guides, oil pump, front and rear main seals, etc., etc. Got the car home and saw what turned out to oil dripping under the passenger side where the transmission meets the engine.

Was hoping it was the valve cover gasket, but couldn't find any leak there, from the head gasket, or any dripping from above. Wiped off the oil and let the car run. No leak. Put the car in gear with the emergency break on, and leak started again.

Does this definitively identify the new rear main as the culprit, and, if so, why would putting the car in gear make it leak. Or could the leak be coming from oil building up in the valley under the intake manifold dripping from a weep-hole at the rear of the engine?

Thanks for any help.

abiby · #2 03-14-2009, 06:30 PM

The obvious question is whether it's engine oil or transmission fluid?

sublettd · #3 03-14-2009, 10:26 PM

Can't answer your specific question, but we just put the rear main seal in the cover today for my engine rebuild that we are about to wrap up--once the driver's side of the block is heli-coiled this week. (Had one thread that pulled out when putting the second head back on. Ugh!!!)

When putting the seal in, my mechanic mentioned that when he used to work at the dealership they replaced the cover instead of reusing it. The reason was that often when removing it you have to pull and tug on it, which causes it to warp.

If you are in fact leaking engine oil this could be the reason. Or, it could be something was over torqued. I'm amazed at the low torque values for so many of the components of this engine--except for the crank bolt, which was 300nm, about 225 ft. lb.

mbboy · #4 03-15-2009, 10:45 AM

Quote:

Originally Posted by abiby

The obvious question is whether it's engine oil or transmission fluid?

Definitely oil!

mbboy · #5 03-15-2009, 10:51 AM

Quote:

Originally Posted by sublettd

When putting the seal in, my mechanic mentioned that when he used to work at the dealership they replaced the cover instead of reusing it. The reason was that often when removing it you have to pull and tug on it, which causes it to warp.

If you are in fact leaking engine oil this could be the reason. Or, it could be something was over torqued. I'm amazed at the low torque values for so many of the components of this engine--except for the crank bolt, which was 300nm, about 225 ft. lb.

I didn't think of that, because I thought the only place oil could leak out of the crankcase was from the rear seal. How can oil leak out of the cover?