Control Circuit and Clutch Slave Cyl. Bleeding with Mityvac?

[jfremder]

I have bled the brakes and clutch twice previously on my '04 R1150RT without incident following the procedures provided here on the discussion board.

 

My question is, why couldn't I use my Mityvac for JUST the control circuits and the Clutch Slave Cylinder, using the servo motor as normal for bleeding the WHEEL circuits?

[ericfoerster]

Seems like that is the case from what I read. JMHO as I've never done it

[Ken H.]

I have bled the brakes and clutch twice previously on my '04 R1150RT without incident following the procedures provided here on the discussion board.

 

My question is, why couldn't I use my Mityvac for JUST the control circuits and the Clutch Slave Cylinder, using the servo motor as normal for bleeding the WHEEL circuits?

I suspect you could, but why?

 

Why introduce another variable into a procedure on a complex system that has been proved out to work?

[jfremder]

Well, three reasons I guess:

 

1) I get to use my cool new tool

 

2) It's a little easier than

pump open close repeat pump open close repeat

pump open close repeat pump open close repeat

pump open close repeat pump open close repeat

pump open close repeat pump open close repeat refill etc.

 

3) A little less likely to mess up the rhythm and get air in the system.

[TKNorCal]

I used the Mityvac to bleed the clutch on a 2002 R1150RT without incident. Note that the clutch lever gets moved full travel in normal operation.

 

I elected not to use the Mityvac with the control circuits because I wanted to move the brake lever full travel to insure that the piston was cleaned.

 

I did not use the Mityvac on the wheel circuits (the part where you use the funnel thingy) because everyone here on the forum said it was a not a good idea. It may also say this in the BMW shop manual.

 

I think the ABS brakes on the L1011 and the MD80 aircraft are less complicated than the BMW evo.

 

Cheers

 

Tandy

[Les is more]

Here's an exerpt from a recent post Jamie (KMG_365) put up that might be helpful.

Rationale: Water is a universal solvent, and an oxidizer (provides oxygen for oxidation, i.e. rust ) and therefore a natural corrosive. New BF absorbs water from the air at an impressive rate (as soon as the seal is broken on the bottle) and this rate of water absorption is accelereted by heating (during heavy or sporting use). If the same water-bearing BF sits bathing the master cylinder's piston as it continues to absorb more water from the air, and the rubber seal in the MC never sees (scrapes, cleans) the remaining 60-70% of the piston during normal use, the last 60-70% of the piston will corrode (rust) and become pitted and rough/jagged. When you neglect to regularly bleed your brakes--then finally do them by bottoming out the lever all the way to the grip--thereby pushing that now cheese grater of a piston into the aging rubber seal--the MC seal (that keeps the BF inside) is thereby frequently ruined and you will now likely need a master cylinder re-build.

 

If the above situation applies to your non-EVO bike, I would use a mighty-vac or other pressure bleeder to bleed the brakes to avoid possible MC failure and subsequent expense and trouble. Remember, however that on the EVO bikes you use the servos to bleed the wheel circuits (not bottoming out the lever), and only pump the lever all the way to the grip (not using the servos) when bleeding the control circuits (every two years). I also feel the need to mention that BMW says you shouldn't use a pressure bleeder on the control circuits either (due to the convoluted plumbing, no doubt). My solution then, since it's so easy to do the control circuits once you've got the tank off to do the wheel circuits every year anyway, is to do them all every year.

 

I use SB's and do NOT use a pressure bleeder. I figure bottoming out the lever/piston in the MC's every year and keeping the BF clean (changing it out every year) keeps the piston clean and the rubber seal from getting torn up. Leslie and I each have over 100,000 miles on our EVO brake R1150RT's (a 2002 and 2003) and we've had no brake, bleed screw or leaking MC issues yet!

[steveknapp]

I thought there was some mention in the BMW service manual for this that forbid the use of the vac bleeder for the control circuits...I could be mistaken.

[Stan Walker]

no, it's in there.

 

Stan

[steveknapp]

Stan, I'm confused...

 

no, I'm not mistaken, the manual says "no"

 

or

 

no, I'm a dufus, the manual says it's OK

 

[Stan Walker]

no, I'm not mistaken, the manual says "no"

 

No, you are not mistaken, The manual say's no to using vacuum extraction on the control circuits.

 

Stan