Can't bleed rear brake

[wendell42]

I am working on a '79 R100RT that was sitting for about 10 years. The rear brake was frze up so I ordered a re-build kit for the rear master cylinder. I disassembled the master cylinder without difficulty and honed it out, cleaned it and made sure the inlet for the fluid was clear. I put the whole thing together but am not getting any fluid through the system. I put a vacuum on the bleeder screw but am not pulling anything through. I disconnected the brake line from the back of the master cylinder and it is sucking air fine. I also checked the flow of fluid from the resivour and that is fine. It just seems that there is no fluid getting through the master cylinder. Am I missing something here? Or is there some "secret" on how to bleed the rear brakes?? Any help would be GREATLY appreciated.

Wayne

[sgborgstrom]

First off I'd repost this to the "airheads" section of this forum, you'll probably get more eyeballs looking at the question there.

Second, try cleaning out the bleed screw itself. They are kind of exposed down there and whatever crud it was that froze the calipers may well have blocked the passageway in the screw.

Steve

[kbasa]

Moved to airheads.

[wendell42]

Thanks for the info Steve, and thanks Dave for moving the post.

The bleed screw is clear and the entire line from the master cylinder to the bleed screw is clear. I took the line off the rear of the master cylinder and was able to use the vacuum pump to pull air through it.

When I pump the brake with the brake line off, there just does not seem to be getting fluid through it. It seems like the fluid is not getting from the reservior through the master cylinder. I have real smooth movement with the piston and nothing is binding. I even took the old piston and matched it up to the new one to make sure it was the right one. Everything matched. The darn thing just seems to not want to pass the brake fluid through it.

Anyone have any ideas?

Thanks!

Wayne

[flash412]

Pull the master cylinder apart again and make sure that the TWO holes are clear. You can see them only after you remove the reservoir.

[lkchris]

Rotate caliper until bleed port is vertical

http://home.jps.net/~snowbum/brakes.htm

[wendell42]

Thanks for the info.

Are the two holes I am looking at in the master cylinder, the resivour or the piston?

[flash412]

Are the two holes I am looking at in the master cylinder, the resivour or the piston?Master cylinder. Sometimes brake fluid crystallizes in the holes. The holes are how the fluid gets from the reservoir to the cylinder itself. One is to let fluid in and the other is to allow fluid to escape as it expands (rather than pressurize your brake system). It sounds like either your piston had the seal put on bassakwards or else the hole is blocked and not letting fluid into the cylinder from the reservoir.