Hydaulic Clutch Bleed Off - Any ideas

[BucksTherapy]

I have a 2006 RT, Apparently this is the first year BMW used mineral oil instead of brake fluid.

 

I just returned from a 10,000 mile trip across NA and back. After some long stretches at high speed the clutch would not release until the clutch lever was almost to the hand grip. A couple of time it went away completely and i had to shift to neutral, stop, pump the clutch lever several times and it would work until the next lond high speed stretch.

I took it to a BMW dealer and they bled it but didn't see any air. They also checked the master and slave to ensure they were holding and they appeared to be once pumped up or when being used frequently.

It is quite disconcerting to be zipping along at 100mph and want to slow down or stop and find you have no clutch.

I have a theory that the mineral oil may be boiling when the engine compartment is running hot. Engine temps are fine and outside temps were not overly warm some of the time this was happening.

 

Any ideas, suggestions? Does not misbehave when I get it to the dealer.

[jmf]

Had a similar experiance on my 06 r1200GS last year. Never got to the point of total non function but was close and i was along way from home or a dealer. Made a 250 mile dash to salt lake BMW. They flushed the clutch system and said they found air in the line. However the problem came back within two days but not as bad. Got back to Austin and the clutch has worked fine every since. Its my belief that riding at higher elevations are linked to losing clutch function in my case. I haven't rode a higher elevation since. But when i do ill be taking fluid and tools to flush myself.

 

Matt

[BucksTherapy]

Its my belief that riding at higher elevations are linked to losing clutch function in my case. I haven't rode a higher elevation since. But when i do ill be taking fluid and tools to flush myself.

 

Matt

 

I was in the Rocky Mountains when it first occured and the second time I was in the Cascades. I hadn't made the connection.

I seek out mountain riding so I am going to have to find a solution for this. I wonder if there is a different kind of mineral oil that would keep it from degassing or boiling at higher elevations?

 

Any chemists out there that can explain this?

[Jim VonBaden]

All R1200 Hexheads have mineral oil clutch fluid.

 

There is no way that the fluid will get so hot as to boil, no matter what altitude. There is nothing contacting the clutch slave or master cylinder that ever reaches the temps needed to boil the fluid, but there have been a few instances of the slave cylinder going bad.

 

Jim

[BucksTherapy]

All R1200 Hexheads have mineral oil clutch fluid.

 

There is no way that the fluid will get so hot as to boil, no matter what altitude. There is nothing contacting the clutch slave or master cylinder that ever reaches the temps needed to boil the fluid, but there have been a few instances of the slave cylinder going bad.

 

Jim

 

The dealer and I have both tested the master by holding the lever at different levels by tying it off and it is not leaking off pressure.

 

What is strange about this to me is why it would act up at some times and not others. I had observed it after long stretches where the clutch was not used when at high altitude.

 

Is there anything that might de-gas out of the mineral oil at high altitude?

 

C'mon you chemical engineers!

[jmf]

Bucks

 

On my GS I was in contact with the local dealer at home as it was happening so they were aware of what was going on. When I got back home the local dealer checked it out and all was well with the clutch and has remained well. It’s a little scary going from riding throw the mountains then coming into a town and having to pump the clutch just to get it to disengage.

 

On my bike the lose of clutch was gradual not a sudden lose. It got to the point that I wasn’t sure pumping the lever was going to get enough pressure to disengage the clutch.

 

 

Wish I had an explanation but there is none that makes since. If there is a leak in the system it should be easy to find. I don’t believe the clutch fluid is getting hot and causing this.(Just my gut thought). I’m convinced the higher elevation is a big part of this but not sure how this fits into the puzzle.

 

Texas doesn’t have much in the way of mountain riding so I haven’t been able to reproduce the situation.

 

Matt

[hopz]

My house is at 6000 feet elevation. I have never had a clutch problem. I think the Altitude theory may be a red herring. Except for the air in the system. At higher altitudes the bubble would expand. But- having said that I just cannot imagine that being the root cause of your problem.

 

I would look to other causes first.

[BucksTherapy]

Bucks

 

On my bike the lose of clutch was gradual not a sudden lose. It got to the point that I wasn’t sure pumping the lever was going to get enough pressure to disengage the clutch.

 

 

Matt

 

This is exactly how mine behaves and exactly the same response from the dealer.

 

I am sure there must be a chemical engineer on this site that could offer some insight into what might be happening. Like you there are no leaks, fluid does not seem to be getting by the o-rings in the master cylinder, it only seems to happen at altitude and fix itself when I drop down off the mountains.

 

The first time was in Banff and the second in the cascades.

 

Any chemical whizzes out there? Is there anything that could be in the fluid that would de-gas at higher elevations?

 

Has anyone else experienced this?

[planepaul]

I have an idea about your phenomenom. My hunch is that when you take it up to the ton (100 mph) for a while, you are making more drive train heat, and expansion is retracting the clutch slave cylinder pushrod. When you slow down you get a cooler operationg temperature that leaves some gap between the slave cylinder piston rod and the throwout. The nice thing about hydraulic actuating systems on bikes is that they "self adjust" to changing clearances. Here, though, the system won't readjust until you give the lever a few cycles to take up the clearance that you generated by going way fast. The key here is whether the system goes back to "normal" after you restore it by cycling the lever. If so, then I think I'm right, and you have a non-problem. Just cycle the lever until you get the feel back.

 

In the old days dirt bike clutches could overheat and expand so much that they would change the disengagement point dramatically (some still do I guess).

 

I can't verify my theory because I have never taken my RT past the ton for any length of time.

 

Paul in CA

'05 R1200RT

[RFW]

I have a theory that the mineral oil may be boiling when the engine compartment is running hot. Engine temps are fine and outside temps were not overly warm some of the time this was happening.

This is definitely not the problem. There is no way that temperatures in the engine can get so hot as to make oil in an external component like the clutch slave, boil! If this were true, then the oil in the crankcase would be at even higher temperature and would also be boiling too.... AND your engine would be way past overheating.

 

Even if there were boiling of the clutch fluid, it can readily expand back into the reservoir. When you release the clutch, fluid can freely pass back into the reservoir, and it is designed this way to eliminate problems such as you are experiencing, where heating causes the fluid to expand.

 

Your problem is almost certainly a blockage in the master cylinder.

[jmf]

One other note. When my clutch stated acting up it was if there was excess play in the lever. Not like there is air in the system that shows up as a mushy fell. Its like there is no resistance for most the travel in the lever. On the 250 mile ride to the dealer I would pump the lever several times every 25 miles or so just to get the clutch to disengage. After the dealer bleed the system all was well till I got back in the mountains.

 

Not saying the elevation is what cause this that’s just when it stated to act up both times. The idea about something expanding or contracting sounds more like what I felt with the lack of resistance at the lever. However I could pump the lever 20 or 30 times and only get half the travel at the lever at best.At its worst i was starting to think i was going to lose the clutch altogether. It was getting that bad.

 

Matt

[BucksTherapy]

Your problem is almost certainly a blockage in the master cylinder.

 

If it were a blockage in the master cylinder why would it go back to normal at lower altitudes or when the clutch is used infrequently?

[BucksTherapy]

One other note. When my clutch stated acting up it was if there was excess play in the lever. Not like there is air in the system that shows up as a mushy fell. Its like there is no resistance for most the travel in the lever. On the 250 mile ride to the dealer I would pump the lever several times every 25 miles or so just to get the clutch to disengage. After the dealer bleed the system all was well till I got back in the mountains.

 

Not saying the elevation is what cause this that’s just when it stated to act up both times. The idea about something expanding or contracting sounds more like what I felt with the lack of resistance at the lever. However I could pump the lever 20 or 30 times and only get half the travel at the lever at best.At its worst i was starting to think i was going to lose the clutch altogether. It was getting that bad.

 

Matt

 

This is exactly the experience I had. That makes two of us. Any others?

[BucksTherapy]

The key here is whether the system goes back to "normal" after you restore it by cycling the lever. If so, then I think I'm right, and you have a non-problem. Just cycle the lever until you get the feel back.

 

Thanks Paul. Once pumped up it only goes back to normal for a short time then the lever freeplay increases again.

After the dealer bled the clutch it went back to normal for two days until I was back in the mountains. In fact the second time it happened I parked the bike at the hotell at 6000' and all was fine. When staring out in the morning the freeplay was back.

It is not a leak as nothign like this has happened over the past four weeks at sea level.

Strange problem but it creates driveability issues when the free play in the clutch lever approaches its full range of motion. All you can do is syncro shift to neutral, pump like a mad @$%^&, then stop or shift your way back to a gear.

I would think more then two bikes have experienced this. If someone has mastered this problem pls let us know. The dealer fixes the problem by bleeding the clutch the problem is the fix is temporary.

 

Thanks for the suggestion Paul.

 

Bob

[Ken H.]

I've got to think bad master cylinder. Nothing else 'down stream' that I can think of would cause it to pump back up when the lever is cycled a couple of times.

[BucksTherapy]

I've got to think bad master cylinder. Nothing else 'down stream' that I can think of would cause it to pump back up when the lever is cycled a couple of times.

 

I was thinking this but now that I am back at sea level and not haveing significant swings in altitude it has been fine for a month.

 

I'm beginning to think that some chemical in the mineral oil or some contaminant remains liquid at constant pressure but when you expose the bike to 8000+ foot changes in altitude over short periods of time then that chemical expands into gas. Once you go back down the incremental pressure transforms this chemical or compound back to liquid and the problem disappears.

 

There must be one chemist or chemical engineer that could tell me if I have lost my mind or if there is a chemical or compound that could be suspended in the mineral oil that would behave like this.