Originally Posted by watchdude1
I checked the rear brake cylinders one had fluid inside the boots I changed with another cylinder i had re bleed the system , the brakes worked ok then I had to stop short again now the brake peddle is down almost to the floor again , they still ar working but not good.
should i replace the rear cylinders or master cylinder don't see any fluid leaking
Seems that you blew a rear wheel cylinder. You changed that and re-bled the system. Since the same thing has happened again, you possibly have blown out another wheel cylinder. Seems likely since they all are probably the same age. When one goes, it is best to replace them all.
Check closely for any leaks in the system. Are all the bleeder valves tightened after you re-bled the system? If the brakes get better after pumping the pedal, you might re-bleed the system again as you probably still have some air in the lines.
How much free play do you have at the brake pedal? If this is zero, you may not have the master cylinder pushrod adjusted correctly and this will not allow the master cylinder to fully return after applying the brakes. You should have 1/4"-1/2" free travel at the top of the brake pedal.
Another thing to check (if you have drum brakes in the rear) is the brake adjustment. If the rear drum brakes are not adjusted correctly, you will have a low pedal.