1978 W123 280CE/ M110.984

Getting ready to replace the Front Main Seal. Wish me luck on that. I was underneath the Benz snooping around today with a flashlight, and inspecting the crud beneath the seal. I noticed that the front of the seal was protruding about 1.5mm from the front of the block. (Gee, no wonder oil was leaking!) It wasn't completely out, but it sure wasn't seated where it should be. Not even leaking enough to drip or puddle.

Now, before I replace the seal, I want to insure that nothing has caused the seal to push itself outward. Since I am the 4th owner (vehicle has 115,000 miles), I don't know if the seal was ever replaced before. I did see in the FSM that the outer edge does require sealant when installed. So it's either possible that the seal has just lived its useful life, it was replaced and no sealant used, OR, something has caused if to pop forward. I'm not noticing any other telltale signs. When I recently replaced my ring gear and had the flywheel removed, only minor signs of the rear main seal seeping were observed. I also just adjusted the valves. It had been a couple of years.

So now the questions for the engine gurus, could a clogged blocked Vent Valve (between the Valve Cover and the wall of the Head) cause enough pressure to unseat a seal? Could improperly adjusted valves cause excessive crankcase pressures causing a seal to push out? Car runs fine, no pressure noticed with dipstick or oil fill cap removed and engine running.

Help is sure appreciated.
MM

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