Recurring gearbox oil leak

[jpod]

Afternoon tossers.

So, a while back the gearbox on my R1150GS was leaking from the input shaft rear oil seal (the one under the clutch slave cylinder) with all of the expected slipping clutch malarkey. After replacing the seal and the clutch and putting it all back together, I didn't make it 100 miles before I felt the new clutch slipping again.

Having read every post I could find here, I was convinced I had done all of the right and clever things, including cutting a little slot in the gasket so any oil could leak out of the recess under the clutch slave cylinder. Unfortunately, this all happened at the start of a month long trip across Europe, in which I completed over 6000 miles with the slipping clutch and leaky seal. Needless to say I became very familiar with the smell of gl5... oh and I'm quite sure that having a catalytic converter there to catch and burn the oil Is the only thing that kept the oil off my tyre and me off the ground.

Anyway, I digress: the point is what do I do? I should add that upon my return, I took It apart again and this time hammered the seal In a bit further to see if it would have any effect. No dice. I just don't understand why this seal would leak in the first place, much less a brand new one. I'm sick and tired of my bike smelling like a sewer.... any advice welcome.

 

[davegs]

Afternoon tossers.

So, a while back the gearbox on my R1150GS was leaking from the input shaft rear oil seal (the one under the clutch slave cylinder) with all of the expected slipping clutch malarkey. After replacing the seal and the clutch and putting it all back together, I didn't make it 100 miles before I felt the new clutch slipping again.

Having read every post I could find here, I was convinced I had done all of the right and clever things, including cutting a little slot in the gasket so any oil could leak out of the recess under the clutch slave cylinder. Unfortunately, this all happened at the start of a month long trip across Europe, in which I completed over 6000 miles with the slipping clutch and leaky seal. Needless to say I became very familiar with the smell of gl5... oh and I'm quite sure that having a catalytic converter there to catch and burn the oil Is the only thing that kept the oil off my tyre and me off the ground.

Anyway, I digress: the point is what do I do? I should add that upon my return, I took It apart again and this time hammered the seal In a bit further to see if it would have any effect. No dice. I just don't understand why this seal would leak in the first place, much less a brand new one. I'm sick and tired of my bike smelling like a sewer.... any advice welcome.

Did you replace the clutch and the friction plate?, see on here using the same friction plate does cause clutch slip after a short milage, do a search.

 

[jpod]

Thanks for your reply davegs. I did indeed change the whole assembly, but that wasn't my point. It's the chronic leak from the oil seal that concerns me; once that is solved I'll replace the clutch but not before.

What I'm after are some cleaver reasons why my seal isn't sealing.

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[fatnfast]

Is the replacement seal a genuine BMW one?
Is the surface the seal sits in free from nicks or marks and does it feel perfectly smooth and spotlessly clean?. Same with the area the seal lip covers. Any deep gouges will cause leaks and repairs would be difficult.
If this is the case you can get seals with slightly greater width which could overcome this for the outer surface.

 

[jpod]

Yes it's a genuine bmw seal.

Having read many posts on this site, I have come across this idea that a scratched surface could cause leaks. It makes some sense to me, so I ran It past an experienced bmw mechanic and he practically laughed at me... said he'd never seen an oil seal leak because of a scratched surface.

I accept that a relatively deep groove could allow some oil to pass, but I get a lot. Can anyone think of any other reason why this might happen?

One theory is that the gearbox breather might be blocked, thus pressurising the gearbox and forcing out oil.

I may have a look at the valve next weekend. If that's OK, I'm thinking of hammering another seal in there. Any thoughts on running with two seals?

 

[GARAGE HERMIT X2]

if there's room for two seal's wont hurt knocking another one in,
not being cheeky, but you have put the seal in the correct way round,

 

[jpod]

I put the new seal In same as the old one (hopefully that was oriented correctly) - flat side out, recessed side with spring facing the oil.

 

[fatnfast]

Yep, seals in the correct way. BMW seal has a ribbed outer to cover any expansion due to heat and as you say thats correct. I'm not sure 2 seals would allow enough room for the slave cylinder plunger to operate correctly? Also be carefull that the seal is not pushed to far back.
Could your existing seal be fitted to far in? Below is a pic I nicked from elsewhere which shows that there is an oilway at the back of the seal tunnel (view is from the inside of the gearbox). If your seal is to far in maybe its getting through this way? I'm sure someone measured the depth previously and posted the info on here.
Is there a presure release valve in the breather? Theres no 'pump' so would there be a build up of pressure to cause this anyway?

 

[Steptoe]

.
Is there a presure release valve in the breather? Theres no 'pump' so would there be a build up of pressure to cause this anyway?

No pressure release valve in the gearbox. Just push fit plastic sleeve that locates inside the gearbox under the rubber breather cap .

 

[Ted]

Sounds just like what I did on my old GSA. Second time I found that both the seals on either end of the shaft had failed allowing oil to run along the clutch actuating push rod and spin up onto the clutch plate. Had to strip it twice and replaced both seals and felt packing on the rod. No more problems till I sold it a few thou miles later. Two seals are one at the clutch slave cyl end and one at the clutch housing end.
Felt is item 5 on right picture. Think seals are 1 & 2 in the left picture.
Hope that helps.

 

[jpod]

Thanks for digging that up fatnfast. Perhaps my seal is indeed too far in, but it was already leaking when it was a half inch further out... I suppose it could have been too far in in the first place.

I reckon there is enough room for another seal. I think that as long as the input shaft protrudes beyond the seal, the clutch slave piston will be well clear.

As far as pressure, if the breather was blocked then the normal expansion of air from heating might create pressure. Though, I have a hard time seeing how the breather would get blocked...

 

[jpod]

Thanks Ted. Did you do anything different between the first and second time? Seal position, seal type, etc..?

 

[Ted]

Yep first time I just replaced the seal in the clutch housing, second time I did both seals. When I took off the clutch slave cyl the housing was full of oil, it should have been dry. Hwve a look at yours if not already.
I did take the gearbox over to the dealers who replaced the seals for me as when I took them out forgot to check how far they were in! They used a correct tool to fit a preset depth. Were very good I just gave the tech a £5 took him 10 min. Worth it for my piece of mind, didn't want to do a3rd strip.

 

[jpod]

Thanks Ted, I'm sure the bmw dealership would do a good job, but I prefer to do it myself.

And, I'm not sure I believe this generally accepted idea that the seal has to sit at exactly the right depth in the tunnel; I rekon it will seal at various depths in the tunnel.

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