BMW K100 leak between clutch and transmission housing

[Belgian]

Hiya all,


I've had my K100 for over 3 years over which I've treated her as I should (spline lube, tb sync, regular maintenance,...). I intend on keeping her for as long as possible! 
Since recently I've had the following problem; I get some leakage between the housing of the clutch and the transmission. It's only on the right side and it does not drip. The clutch still works fine.
Has anybody got an explanation for this?


An afternoon ride will give me this:

[Martin]

There is a weep hole right at the bottom of the joint between the engine and the gearbox. Check to see if this is blocked, this is where oil normally appears if you have leaking seals or "O" rings.
Regards Martin.

[Belgian]

Hi Martin, thanks for your reply! The weep hole below is clear and totally dry.
Any idea what could be the cause?

[Martin]

It could be coming from further up. Bricks do have a problem with leaky fuel tank seams. You could try placing paper towel in and under places you suspect that are leaking leave overnight and check. Spray on talcum powder is also good for chasing leaks, clean the suspect area let it dry the spray with the talc and wait for leaks to show. Leaks sometimes originate from further away than where they appear.
Regards Martin.

[Laitch]

Any idea what could be the cause?

What does it smell like? On the menu is gasoline, transmission fluid and oil. If you have a wet cell battery, the overflow and gravity could be carrying grime down that seam then evaporating.

[Belgian]

I took my time to really check and it's not coming from the exterior.
It comes from the inside, that is sure. Not possible to say whether it's gearbox or motor oil.
Should I be having nightmares of rear main seals and O-rings?

[Laitch]

Not possible to say whether it's gearbox or motor oil.
Should I be having nightmares of rear main seals and O-rings?

It's possible if you take a whiff of the residue. The two fluids have different odors. As far as having nightmares, do it!

[Belgian]

It's possible if you take a whiff of the residue. The two fluids have different odors. As far as having nightmares, do it!

It didn't have the typical gearbox oil smell, but I'm not saying it isn't gearbox oil.
It's not pure oil but seems to be mixed with particles, which may alter the scent.
That's a bummer  :yow , does the clutch have to be replaced as well (regardless of how thick it still is)?

[Martin]

Leaks in that area normally show up at the weep hole. If it was mine I would give it a really good clean and then ride it for a while, and check if and how much it is leaking. I suspect a very minor leak and I would not be too concerned, one tiny drop of oil can spread and look huge. I had had occasional drips coming from my weep hole, and on pulling it apart none had got onto  the clutch plate.
Regards Martin.

[Belgian]

Leaks in that area normally show up at the weep hole. If it was mine I would give it a really good clean and then ride it for a while, and check if and how much it is leaking. I suspect a very minor leak and I would not be too concerned, one tiny drop of oil can spread and look huge. I had had occasional drips coming from my weep hole, and on pulling it apart none had got onto  the clutch plate.
Regards Martin.

Your reply made me feel a little at ease.
I cleaned it earlier and went for a ride and it becomes slightly visible after 100 kilometers (60 miles).
By that I mean you start seeing the black stuff between the seam.
In any case I have not seen anything drip from the weep hole (ever). The hole itself remains very dry.

[Laitch]

That's a bummer  :yow , does the clutch have to be replaced as well (regardless of how thick it still is)?

Do you have a maintenance free battery? You never made that clear.

 Go ahead and have the nightmares though. You'll feel better when you wake up and nothing is wrong.

[Belgian]

Do you have a maintenance free battery? You never made that clear.

 Go ahead and have the nightmares though. You'll feel better when you wake up and nothing is wrong.

I have a maintenance free battery indeed 

[Laitch]

Clean the seam on the case. Sweet dreams.

[Belgian]

Thank you Laitch and Martin!

[Martin]

Keep riding it, clean with a degreaser and soap and water a couple of times then keep an eye on it. It's very hard to determine the type of oil with that small amount.  At a cost (possibly only one arm or half a leg) it would be possible to have it analysed. 
Don't worry be Happy or one of the other dwarves.

[The Mighty Gryphon]

Gravity will probably prevent oil from the rear main seal or the input shaft seal of the transmission from getting to where you are seeing it.

Rather, I would suspect it is coming from one of three possible places: a cracked crankcase breather hose/airbox, the starter o-ring, or the alternator drive.

You will need to pull the battery and possibly the starter and alternator to really see where it is coming from.  In any event, that seepage is merely an annoyance and probably doesn't represent any immediate danger to the engine.

[Martin]

I'd still try placing paper towel above the area where you have the leak but not touching the leak. Do it after a long run while the engine is hot. also due to capillary action oil can and does run up hill. In your photos I can just see the engine cover  a small weep could run back from this cover and with capillary action run up.
Regards Martin.

[Laitch]

also due to capillary action oil can and does run up hill.

Why does the oil can run up hill?

Certainly it isn't to fetch a pail of water.

[Martin]

It needed a change. :hehehe

[Laitch]

 :kill-sword-dueling:

[Martin]

Touchez

[bocutter Ed]

Why does the oil can run up hill?

Because it can