1984 r100rs rear brake bleeding

[dkilmer]

I just rebuilt the rear caliper on my 84 r100rs and for the life of me cannot get it to bleed properly, I took off the caliper and held it higher than the
master for a day and seems like I got all the air out, but still spongy
does anyone have a hint?
thanks

[Friedle]

Scroll down to the post of 12-31-05 for a good set of clues to your problem regarding brake bleeding procedures.

:doh

Friedle

[bmwmick]

I just rebuilt the rear caliper on my 84 r100rs and for the life of me cannot get it to bleed properly, I took off the caliper and held it higher than the
master for a day and seems like I got all the air out, but still spongy
does anyone have a hint?
thanks

You 'could' try one more thing, empty the reservoir and then push the pistons back all the way in the caliper. Sometimes this will force persistant air bubbles back to the master cylinder. Once the pistons are all the way back, mount the caliper on the rotor and slowly pump the brakes back up (while watching the fluid level in the reservoir). This has worked several times for me.
If there are any wear grooves on the rotor and you have new pads, the pedal WILL feel spongy for a few hundred miles till the new pads take on the grooved pattern.

Hope this helps....

[mcar]

Oak says you have to turn the caliper upside down so the bleed screw is on top.Hang it with a coat hanger or wire from the frame,I havent tried it on mine yet,but have read his column in "Airmail"

[Polarbear]

I did a friends R100rt years ago and it was one of the worst Beemers I've ever had to bleed. The rear brake line runs down and up and around and all over, it seems before it gets to calipre. This creates a lot of room for air, if one drains system. Your RS is probably same as RT. I finally used a good vacume pump and forced fluid through rear system and success came quickly. Some brake fluid changes go just fine without the use of a vacume pump, but this one model beemer's rear brake lines absolutely needed the pump. You can buy these pumps at most (better) auto supply houses. NAPA,etc. Get a good metal one, if choosy, because the plastic ones fail after some hard use. Happy wrenching...R/Polarbear

[Stuff2C]

Now get ready to rebuild the master cylinder. Because once you push the piston past it’s normal stopping point more than a couple of times, you rake the rubber on the plunger over the ridge that builds up over time and it starts to leak.
If it doesn’t…get a lotto ticket. :)

[Bigrider]

I kow it sounds counter intuitive, but I place the brake caliper on ground, or as close to it as possible, the bubbles will slowly (and I mean very slowly) work their way up. I block the brake pads so that when I put pressure on the pedal the pads don't move and the fluid of course goes toward the caliper, but when I release, the vacuum seems to suck up the air bubbles close to the master cylinder. I think using a syringe to pressure the new fluid up from the caliper may be a better way to get the job done.

Dave H
Colorado Springs Co