rear brakes nightmare

[SeanMora77]

I wrote that wrong. Fluid doesn't spurt out until I depress the brake lever.

[sedelen]

I wrote that wrong. Fluid doesn't spurt out until I depress the brake lever.

OK then, try to bleed them, put a little pressure on the pedal and open the bleeder a little then push the brake all the way to it's stopping point, once there tighten the bleeder and let the pedal come back then do it all again until you get all the air out.

Once you feel confident you got all the air out through both bleeders, press down on the brake and see if the caliper closes.
I had a stuck piston on my front brake once, I squeezed the lever and whacked the caliper with a rubber mallet. Actually that worked.

[SeanMora77]

I'll give it a shot. I'm confident that the pistons aren't stuck because I popped them out with compressed air when I rebuilt them, and scoured the gunk out of the caliper. If I remove the dust cover from the top of the caliper I can see the pistons actuate when I move the brake lever.One thing I did not do was replace the piston seals. I removed the old ones and cleaned the groove they sit in and put them back in. Is it possible they are too worn to offer the resistance needed? The only reason I reused them is because they looked fine after I cleaned them and I read that there is really no need to replace them.

[sedelen]

I'll give it a shot. I'm confident that the pistons aren't stuck because I popped them out with compressed air when I rebuilt them, and scoured the gunk out of the caliper. If I remove the dust cover from the top of the caliper I can see the pistons actuate when I move the brake lever.One thing I did not do was replace the piston seals. I removed the old ones and cleaned the groove they sit in and put them back in. Is it possible they are too worn to offer the resistance needed? The only reason I reused them is because they looked fine after I cleaned them and I read that there is really no need to replace them.

I would think if they were bad you'd be leaking fluid.

[sedelen]

Somehow we got to isolate the function of the master cylinder and the caliper.
If you can get a steady flow of fluid from the bleeder and you pump the brake it would seem to me the master cylinder is pumping, and when you tighten down that bleeder screw you should have some pressure there.
So if you have the bleeder screws closed and pump down and hold it and loosen the screw it should be under some pressure when you loosen it.
If you're confident it's working then you need to look at the caliper, the pistons, the pad installation, could be binding mechanically.
Perhaps something in the links below will help sort things out.

http://members.dslextreme.com/users/bikecliff/images/bleedbrakes.pdf

http://members.dslextreme.com/users/cbsaunders/gs/79-Brake_overhaul.pdf

http://members.dslextreme.com/users/storagecliff1/images/brake_caliper_overhaul.pdf

[SeanMora77]

Well, I removed the rear brake line from the frame (again) and elevated it higher than the MC and bled. No bubbles, still no building pressure. I'm going to just assume that the line is shot at this point. I ordered a new one last night, once I get it and install it I will let you know the results. Thanks again guys.

[subforry]

I am thinking that the pistons are sticky and springing back into the caliper.

I had this problem with my front calipers. They were cleaned and it felt like the pistons went in fine, but they were sticky. What happens is that most of the mechanical movement of the lever goes to moving the pistons. Then when you release the lever they move back into the caliper. It feels just like there is air in the line.

I fixed the problem by getting new pistons and very carefully cleaning the seal groves in the caliper.

Get a hose crimp tool (or make one). Crimp the hose and I bet you will find the MC lever is hard as a rock.

[SeanMora77]

The saga continues... I bought a new SS brakeline, installed it today. No dice. So then just out of curiosity I pulled the rubber boot off the MC and there were the seal and snap ring. I took the MC apart again and found that the seal was bent, so after a couple hours of carefully tweaking it back into shape I re assembled everything. Still no dice. I can see the pistons moving in the caliper. Getting real frustrated. Im going to try the rubber mallet method, hopefully a sticky piston. That's about the last hope.

[Nessism]

Order of assembly.

[SeanMora77]

That contradicts everything I've read. If that is the order of assembly than I need to tear the MC apart again.

[sedelen]

That contradicts everything I've read. If that is the order of assembly than I need to tear the MC apart again.

I would bank on Ed's advice, besides what do you have to lose at this point?

[eil]

Ed's picture is how mine is put together as well. (I still have the picture of mine on my phone)

[SeanMora77]

True, I have nothing to lose. At this point I can have the MC torn apart in no time... Ill give it a shot. Thanks again

[SeanMora77]

Gentlemen, we have brakes!! When I opened up the MC the little rubber cup was sideways halfway up the spring, and the little hat looking piece was stuck to the spring. I re-assembled in the order you showed me, primed the MC, bled once and the brakes are solid as a rock. Thank you thank you thank you. I will now be able to sleep soundly at night. As for who ever told me the completely wrong order in which to re assemble, well, Im not going to go digging through my old posts to pinpoint the giver of wrong info but for future reference the order you laid out for me is 100% correct. You guys rock, thanks again!

[eil]

Awesome! Glad you were able to get to the bottom of it.