VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Can too much oil cause rear main seal to leak?

I mentioned in an earlier post that my rear main seal is leaking badly.

I just realized that according to the dipstick, there is approximately 1/2" overfill beyond the full mark on the dipstick, so I'm wondering if the former owner may have overfilled the crank and this is a contributing factor to the rear main seal leak? This may be wishfull thinking on my part.....

I should have been keeping a closer eye on the actual level on the dipstick, but was mainly keeping an eye when to add oil which has never yet occurred after approximately 200 miles of driving. Also need to do an oil change anyways.

I did perform a complete tuneup on the car last week (points, plugs, plug wires, dist cap, rotor, condensor) and the car now runs great with no more "stumble" so I feel pretty good about that.

Haven't had a chance to work on the rusted emergency brake cables, but plan on tackling that project next and will report back on that.

I did replace the old rusty radiator cap with a 4 lb cap. I realize that the car should have a 0 lb cap, but O'Reilly's only had the 4 lb. Question: Is is ok to run a 4lb cap? My radiator appears to be in good shape.

Bob

Bob,

I doubt that the oil level would make any difference unless the crankcase is filled to a level above the bottom of the seal. Some excess splashing may help feed the leak/seep, though.

I acquese to better knowledge. Gene, Chipper, Old216, Uncle Ed, Ray, et al?

Charlie

Bob,

I have found that the best penetrating fluid is used/new automatic transmission fluid. Just coat the lines with this a few times (three or four)and let them sit over night. They should free up, if not do it again. Also try tightening the lines up a little at the transmission, but do it only a couple of turns then loosen it.

Don't beat yourself up if a line brakes, you can buy new ones, and it is better to have a line brake now then when you need to use your emergency brakes.

A lot has been posted on rear seal leaks. Try to do an Advanced Search on the topic. If you need help let us know and we will go over the steps with you.

Good luck, Mike

If you want to drive without a sealed cap, buy one of the pressure ones with a lever on the top. You can install the cap and leave the lever up and turned and there is no way it can close to allow pressure.

Check my post under sealed cooling system.

The rear main can leak on a pre 1940 model that has no rear main seal if the oil is overfilled and car parked at a steep angle with the front elevated. Chevrolet even had a TSB on this in 1939 pertaining to grain trucks unloading.
That small amount of oil you mention will not cause leakage on a 1940 unless the seal is destroyed and the car parked for an extended period of time as described above.

I noticed that my radiator has an overflow line running from the filler neck. I assume that the radiator was replaced at some point in the recent past since it appears to be in very good condition with no bugs, debris or bent fins.

That is correct. The 1940 was the first year for the overflow tube to be in the filler neck.