help-rear brake problems

[roadkingdresser]

the rear master cylinder was pushing fluid out the rear of it. took apart and didn't think it was worth rebuilding. ordered a new Kelsey hayes type. put in on and filled with dot 5 fluid. pushed the fluid from the rear to the cyl.  pumped up and bled a couple times. can get pressure after about a dozen pumps. problem is after I pump it up and get pressure and let off the pedal the cylinder fills up with fluid-pretty fast. any ideas?

[dirtymike]

Is this your 66 Flh that has the brake problem. I would gravity bleed the system for a hour or two.when you get a good pedal feel seal it up and lock the brake down for the night and check it in the morning. Dirty

[JW113]

Sounds kind of like air in the master cylinder. Usually you need to "bench bleed" them before putting on the brake line. You do this by running a hose from the master cylinder output, do a loop, and put the end of the hose in the brake fluid in the reservoir. Then pump the brake a whole bunch of times until you stop seeing air bubbles coming out the hose. That means the master cylinder is clear of air. THEN hook up the brake line, and bleed the system as normal.

-JW

[packrat56]

 
    I've done them both ways, Its a lot faster to bench bleed first.
      packrat

[JW113]

You see these kits everywhere, like Pep Boys, AutoZone, Car Craft, O'Rileys, etc. Usually in the "Help" section.

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-JW

[roadkingdresser]

No it's not the 66. I'm helping a friend with his shovel. Just a bunch of parts thrown together. Hardtail has an aluminum brake setup on the rear mounted upside down. Not sure what brand, no markings on it.  Everything looks good though. Have to try the bench bleed today. I'll let you know what happens. Thanks guys.

[JW113]

Whoa. Hold on. What does "mounted upside down" mean? Which way is the brake bleeder valve pointed on it?

If it is pointed down now (from being upside down) or any othe direction that UP, you have to bleed it off the bike with the bleeder valve pointed up, or you'll never get the air out of it.

-JW

[roadkingdresser]

Yes it is upside down with the bleeder pointed down. Did the bench bleed and was still the same. Took the caliper off and tried the brake, it was working enough just to stop the wheel on the lift. I took it apart and couldn't push the pistons in  by hand.I sprayed some choke cleaner on the pistons and took a small sea clamp and pushed both in. Left the caliper lay on the lift and shot fluid from the rear to the front. Works like a champ. Thanks for the help.