Flywheel Seal Leak Fixed / A Cautionary Tale

You may remember that I replaced the flywheel seal in my 78 SC while I was doing some other work on the engine. The seal promptly leaked. Thinking I must have done something wrong, I ordered another seal, and underwent the fairly significant task of replacing it. The new one leaked at exactly the same rate!

Before digging back in, I wanted to first try to figure out the problem. Lots of suggestions were given, such as a grooved crankshaft end (I knew that was not the problem), too much crankcase pressure (not a likely problem), too much oil pressure (I don't think that can cause the problem).

As it turns out, there are actually 2 different part numbers for the '78-'89 seal. This was a fact that is apparently not very well known. One part number is for an all black seal. The other number is only slightly different (the 3 digets that are 3rd-6th from the end of the part number) are different. This is for a seal that is half black, and half brown. The brown is Viton, and is on the inner part that seals up against the crank. There is hardly any price difference between the 2 parts (less than $5).

Using the viton seal solved the problem!

Replacing this seal is not that uncommon, as most people do it whenever they have the engine out of the car for replacing the clutch, etc. You can save yourself alot of potential headache by INSISTING on the viton seal. Be careful, because lots (most??) places sell the crappy old all black seal!

Brian

Brian,
I am in the middle of doing a clutch job on my 87' 930. I used an all brown seal. I used some loctite around the outside edges to help seal up. Does this sound like the right seal?