Oil Leak Mystery

[dezine2000us]

My LT has been leak-free for all of its 28,000 miles. It was garaged, and on the center stand, for 3 weeks. Then mysteriously, into the 3rd week, it suddenly started dripping oil from the seam in the bell housing just behind the center stand. David Shealey did a long distance diagnostic (thanks again David) and suuspected a leaking engine seal. I drove it out to Bob's BMW and they agreed. The estimate to repair this (and the "probably contaminated clutch") is approx. $1,200. GULP! Unhappily, I made an appointment for a few weeks out, rode home and placed her back up on the center stand to wait it out.

Now the mystery deepens... The leak has stopped just as suddenly as it started. The sight glass shows the oil is still topped up OK so it's not empty.

I started the bike up thinking that maybe the pressure would start the oil leaking again. But it's still dry.

Doesn't this sound like an overfilling problem?? But how can that be when I haven't added any oil for months? Could anything else cause it to start/stop like this?

Any ideas? I sure don't relish spending all that money fixin' what ain't broke.

Thanks for your thoughts.

Joel Adler
White Hall, MD

[eljeffe]

Joel,

I found my rear main seal leaking 4 hours into the trip to CCR. While it was always in the back of my mind for the entire 4000 miles of that trip, it didn't stop me. Every once and a while, the clutch would spin up -- some days were worse than others -- but the grand old lady kept running. I just watched the sight glass and kept going.

BTW, I've got a friend that has a K1200RS. His has leaked on and off for over a year now. Until it starts causing your clutch to slip or you have to carry a case or two of oil with you on every ride, I'd probably let it go.

BTW, your estimate seems about $500 light. If the seal is leaking, you can be damn sure that there is some contamination of the clutch, and that $1200 will become $1700. And if you have it torn down that far, make sure the mechanic takes a close look at the slave cylinder. An extra $135 can save you another tear down later.

[dshealey]

An engine oil seal leak is far less likely to contaminate the clutch than either the transmission main shaft seals or the slave cylinder.

Engine oil leaking at the main seal has a difficult time getting to the clutch, as it is slung outward by the clutch drive plate and collects all around the housing, and can only get to the clutch area if it just happens to build up enough to drip from the top of the housing through one of the holes on the drive plate and into the clutch assembly. Normally, the oil slung out will just slowly make it's way down around the housing to the bottom, where you now see it.

Either transmission main shaft seals or Slave Cylinder leaks lead directly into the clutch area, and will get onto the clutch parts before showing themselves as an outside drip.

If you see an oil leak, and the clutch is not slipping under hard acceleration, it is most likely the engine seal/"O" ring.

[dezine2000us]

But what would explain the sudden start of the leak? If it's an engine seal leak, why would it be dry for the first 2 weeks on the center stand and then start dripping in the 3rd week? And, what would make it stop leaking when there's still plenty of oil in it?

I certainly won't replace the clutch unless it's contaminated and, hopefully per David's analysis, it won't be.

[dezine2000us]

I just noticed the post counts for the 2 replies I've gotten so far. Jeff with 6,691 posts and David with 7,588. Always there and helping. You guys continue to amaze me with your willingness to share your extensive knowledge and talents so generously.