Bleeding rear brakes - UPDATE

[WoodyFL]

Rebuilt the rear caliper by putting in new seals and cleaning the pistons. I've gone through half a quart of fluid and still getting air. I can see the pads clamping on the rotor when the pedal is pressed, but really mushy pedal.
Not seeing any leaking of fluid anywhere.
Perhaps the new seals got damaged during installation? I would think if that's the case you'd have a leak.

Any ideas guys?

Bob

[bill-jr]

Bleeding them the okd fashoned way or with a vacuum ?

[WoodyFL]

Old fashioned way.

[gordonv]

What did you do about the whole system, did you remove any lines, flush the whole system, etc.?

I figure air is getting back in, somewhere. If you removed a line, then it isn't back on tightly enough.

There was someone else who had the pressure valve in the master cylinder need fixing, if I remember correctly.

[WoodyFL]

The only line I removed was the one feeding the caliper. Put 2 new crush washers on. Was working fine prior to rebuild but I wanted to rebuild due to the pistons being gunked up.

[mello dude]

Rebuilt the rear caliper by putting in new seals and cleaning the pistons. I've gone through half a quart of fluid and still getting air. I can see the pads clamping on the rotor when the pedal is pressed, but really mushy pedal.
Not seeing any leaking of fluid anywhere.
Perhaps the new seals got damaged during installation? I would think if that's the case you'd have a leak.

Any ideas guys?

Bob

Speedbleeders

[sandy]

If you have an air compressor, Harbor Freight has a vacuum bleeder kit. It's about $30 and makes bleeding much easier.
Your bleeding method needs 2 people. Are you holding the pedal down HARD as you open the bleeder?

[WoodyFL]

If you have an air compressor, Harbor Freight has a vacuum bleeder kit. It's about $30 and makes bleeding much easier.
Your bleeding method needs 2 people. Are you holding the pedal down HARD as you open the bleeder?

Yes, my wife has helped me bleed both front and rear when changing fluids for routine maintenance, so she's done it before. I may try the speed bleeders and see what happens. If I can't get rid of the air then I'll tear it apart once more and see what it looks like.

[Daniel Meyer]

Pull the rear caliper and orient it so that the bleeder is the highest point (you can put a block of wood or such between the pads to keep the pistons from moving outward.

It also helps if you pump the pistons reasonably far out (again, use a thinner block so you don't "pop" one) and then clamp/squish them back in with the bleeder open and at the highest point.

[WoodyFL]

Thanks for all the suggestions. I'll get back on it this weekend and let ya'll know how it went.

Bob

[RWhitehouse]

The rear can be tricky. Had same issue after rebuilding the caliper on mine. It worked OK, I could lock the wheel, but pedal had way more travel and felt squishy. Tried regular bleeding, vacuum bleeding, wasn't getting any bubbles out. Finally undid the rear caliper, cut the ties on the hose, and held up up toward the passenger seat with the bleeder up top. Did a few more rounds of old fashioned bleeding and got a ton of bubbles that must have been trapped in the essentially horizontal hose between the m/c and caliper.

[Jersey]

Air can get trapped in crevices and make it impossible to bleed. Good advice being given to reposition (with blocks) so you can work the air out of the corners.  Speedbleeders are SO much easier, especially for the clutch!  A Mityvac might be a good investment.

[da prez]

  What Daniel said is called reverse bleeding. It will work and remove the air. When you push the piston back , do it rather quickly. Be sure the master cylinder is on the low side. The brake hose should be the highest point when you push the piston back in.

                                da prez

[mello dude]

Air can get trapped in crevices and make it impossible to bleed. Good advice being given to reposition (with blocks) so you can work the air out of the corners.  Speedbleeders are SO much easier, especially for the clutch!  A Mityvac might be a good investment.

I have screwed around with a lotta bikes, and I while I do have a good mitivac too, I wont even think about doing a fill/bleed without the speedbleeders. Typically I will start the fill/bleed with the mitivac, and then work the speedbleeders to finish. - Hint on the speedbleeders, go sloooooow, feel the fluid moving.
I zip tie the clutch and front brake levers back over nite once I think I have a good bleed. The levers get solid like that... Havent done a brake pedal...

GL

[WoodyFL]

Got the speedbleeders on order. Will try all of the above methods and hopefully will have success this weekend.
I'll post with the results.
Thanks again for all the suggestions.

Bob

[turtle254]

Got the speedbleeders on order. Will try all of the above methods and hopefully will have success this weekend.
I'll post with the results.
Thanks again for all the suggestions.

Bob

What's the part number on the speedbleeders

[mello dude]

Got the speedbleeders on order. Will try all of the above methods and hopefully will have success this weekend.
I'll post with the results.
Thanks again for all the suggestions.

Bob

What's the part number on the speedbleeders

http://www.speedbleeder.com/

[WoodyFL]

Well, I found out what the problem was this morning. After trying numerous ways to bleed I decided to take the caliper off and inspect it. I could immediately see tiny bits of the rubber seals. Pulled the pistons and took off the seals and found some damage to the seals.
It appears that I hadn't cleaned the seal grooves out good enough and the seals could not seat all the way.
I had ordered new seals and for good measure, new pistons.
Took some 000 steel wool and really cleaned the grooves, installed the new seals and pistons, bled the system with the new speedbleeders and voila!
Problem solved.
Need to make sure in the future to really clean those grooves good.

Thanks for all the advice gentlemen!!   


Bob