Does My Car Have a Rear Main Seal Leak?

rear main bearing seal leakI own a Chevrolet S-10 pickup with approximately 115,000 miles on it. I noticed an oil leak and If I’m correct its coming from the rear main oil seal.

What do you think is the estimated cost and time of repair? If I choose to have this done do you recommend anything else that should be replaced since the transmission will be removed.

My other question is, will too much transmission fluid in the transmission cause damage?

Thank you for your time, I look forward to hearing from you.


Howdy there Mark,

Just off the top of my head I would estimate the rear main seal to be about $675 parts and labor at $75 per hour labor rate.

I would first buy 2 cans of CRC BrakeKleen brake parts cleaner from your local auto parts store and clean off all the oil spill area on the engine so it’s clean and dry. I use that stuff because it is non flammable, dries fast and dissolves immediately without water or wiping.

Once the area is clean and dry, run the engine and watch the suspected area for leaks. I have been fooled by leaks generated higher up on the engine like from an oil pan gasket or even a valve cover gasket or oil sending unit that runs down the engine and drips at the rear near the rear seal.

When any engine oil leak is present I always inspect or replace the PCV valve which helps vent the internal engine air pressure. A valve that is dirty and restricted will not vent the engine properly which can cause additional pressure on oil seals and gaskets.

Too much transmission fluid or too much engine oil can produce an excessive amount of pressure on seals and gaskets as well and the proper fluid level should be maintained.

If I had the transmission out of the vehicle I would also replace the front pump seal on the transmission and inspect the flywheel for any damage or excessive wear on the teeth and replace as needed. I would also check the engine and transmission mounts for wear and damage and replace as well as needed at that time.

Too much transmission fluid can blow out the front pump seal ON the transmission, but will not cause any issue with the rear main ENGINE OIL seal. The two are not related.

Please share this with your friends,

Austin Davis

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