K75 rear master cylinder leaks

[hansrt]

I have a 95 K75 RT (ABS) with a leaking rear master cylinder. The cause of the leak was a pedal that traveled farther than normal. I ordered a rebuild kit from beemerboneyard. My question: Is there anything I have to hone or sand inside the cylinder so I don't mess up the seal again or do I just clean out the bore and install the new seals? Thanks Dean

 

[mrich12000]

Masters care

Straight forword repair.
Take the master off the bike clean the outside witn Brake cleans ) avalable at Nappa) pull the boot follow the chilton or Claymors disasemble check the bore for burrs , clean with, the brake cleans. Use the new kit and reasemble use a little type 4 brake fluid on the asembled center section slowly install install the outer boot install on the bike then follow the bleeding process . good afternoon project.
also a small amount of Bailey Bristol go's good to with this project

ps ajust the brake lever to your foot setting.. \ anyone else has any good ideas?


Mike R..

 

[BUDDINGGEEZER]

brake master cylinder

I just recently rebuilt the rear master cylinder on a K100 Lt. Non ABS, but should not be any different in reguards to your question. Yes, the cylinder should be honed or cleaned up. I did not have a hone small enough so I used a dowel and 320 grit sanpaper and finished with 600 grit. (What I had at the time). The cylinder should be smooth. I was concerned with mine because it was scored worse than other cylinders I have worked on. Mine was not totaly smooth, but it has not keaked for around a 1000 miles.

 

[hansrt]

Thanks Mike and Bgeezer for the tips. I did end up honing the master cylinder and installing a new piston kit. I cannot get the pedal pressure to stay. I used a pressure bleeder to bleed the system. Everything went well, I bled the ABS modulator first, and then the caliper. I then checked the pedal pressure and it was right there. The problem is every time I release the pressure in the power bleeder container, and put the cap back on the master cylinder, I have no pedal pressure. Any thoughts on what I might be doing wrong? Should I finish the bleed with the pedal? Thanks.

 

[mrich12000]

You may need to have the system BMW'd. looks like the system is working but the ABS modulator is not clearing itself of air. Sorry.

 

[BUDDINGGEEZER]

brake bleeding

I don't know how the ABS effects the pedal pressure not staying up. Doesn't matter on a Chevy truck.

try the pedal. Be sure to close the bleeder valve when releasing the pedal. Open/press pedal down/close/release pedal/ repeat untill all air is out of system.

If it won't hold then you probably need a new cylinder.

As I stated mine was not really smooth, but has held for 3000 miles.
Sometimes I get lucky.

 

[hansrt]

brake bleeding worked

Thanks BuddingGeezer for the tip to bleed it using the pedal. It worked and I was extremely elated. My wife also sends her thanks (safety you know). Have a great weekend.