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K75S Bled front brakes, now system appears to leak. Eek...


Neil_K

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I bled the front brakes on my new to me K75S (87). THis was my first experience doing this, but I followed Clymer and my pals with prior experience. THe brakes now work far better, and the fluid is far prettier. Except... I now appear to have leakage from somewhere under the front reservoir. I thought I had overfilled the res. and the warming of the day caused expansion (I live in VT...45 this am, 65 this pm), so I removed a little fluid from the res. I think there is still a seep coming from the seam between the mount and the front cylinder. Familiar? Can anyone help on this one? Should it go to the local BMW guys?

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A leak should have nothing to do with your bleeding the brakes. Bleeding the front brakes in a K75/K100 is simplicity itself ....open bleeder, squeeze brake lever, close bleeder, release lever, repeat.

 

None of these actions can cause a leak at the master cylinder or its reservoir.

 

Likely as not, you are seeing the residuals of a spill when refilling the reservoir.

 

Brake fluid is water miscible (easily mixes with water). With a hose set to produce a nice gentle stream of water, throroughly hose the area around and under the reservoir. This will wash away all residual brake fluid. Then once it dries, see if the "seepage" returns. I'll bet it will not.

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A leak should have nothing to do with your bleeding the brakes. None of these actions can cause a leak at the master cylinder or its reservoir.

 

Some people who seem to know what they are generally talking about have claimed that when squeezing the brake lever to pressurize the brake fluid, the master cylinder piston can travel further into the bore than is normal for regular braking operation and damage the seal, resulting in just the type of slow leak the OP mentioned.

 

Hasn't happened to me but I have read about it several times.

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Any idea of the remedy?

 

One thing that I've tried in the past that worked was to disassemble the master cylinder, clean out the inside of the bore with 0000 steel wool and carefully cleaned off the lips of the seals. Worked fine after that. No guarantess that will work but for the money it's worth a try.

 

When you have the cylinder apart, note the location of the hole to the reservoir in the top of the cylinder. After putting new fluid in and when bleeding, be sure that that hole is as high as you can get it to let the air out of the cylinder while bleeding.

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