Sounds like the rear shoes are not adjusted out far enough. If your parking brake cables are free, apply the parking brake, then pump the service brake a few times. If the pedal is better, readjust the rear shoes.
Did you put the shorter linings on the front side of the rear brakes? Putting the two shoes on backwards will not cause a low pedal in itself, but you'll need more pedal pressure to stop.
Why did you replace the wheel cylinders? If they were leaking, did the master cylinder run dry and draw in air? Once refilled, you can get the air out by pumping the brake pedal part way down, holding it for a few seconds, then releasing it. When you release it, the air bubbles in the steel lines will get pushed back into the reservoir. I had a car that had an empty master cylinder every spring after being stored for the winter. Just filled the reservoir and drove it. Within a few mushy stops, it self-bleed and was fine for the rest of the summer.
How did you bleed the rear brakes? If you gravity-bled them, there's probably air in the lines yet. If you pedal bled them with a helper, how far did you push the pedal down? I made a real big deal with my students to never push the pedal more than half way to the floor. You will run the seals in the master cylinder further than its normal range of travel into the crud that builds up in the bores and rip the seals. Proof that that's what happened will be a pedal that sinks slowly to the floor while you hold steady pressure on it.
Do you have anti-lock brakes? If so, some systems require the Chrysler DRB3 scanner to operate the valves to bleed the system. This should not be a concern if you never ran the master cylinder out of fluid.
Any chance the fluid got contaminated with a petroleum product? Two common sources are repacking wheel bearings with grease, then using your greasy fingers to push the rubber seals back into the master cylinder fill caps when you fill the fluid. Another way is to wipe out a funnel that was used for engine oil or transmission fluid, then use it to fill brake fluid. There's still oil residue in the funnel. If the cap seals are mushy and too big to put back in, there's contamination and ALL rubber parts must be replaced and all steel lines must be flushed and dried. Rubber parts include front and rear hoses, master cylinder, calipers and wheel cylinders, combination valve and height-sensing proportioning valve, (they have rubber o-rings), and the ABS hydraulic assembly and pump if you have ABS.
I assume there's no brake pedal pulsation or you would have mentioned it. A warped rotor or bent hub can push the caliper piston back in resulting in more pedal travel. You would not notice the low pedal until you drove it. Egg-shaped drums will do the same thing to the wheel cylinders.
Check the parking brake struts on both rear brakes. Both shoes must be against the big anchor pin on top, and you should be able to push the strut rod with your thumb to compress the anti-rattle spring at least 1/16". If either of these are not true, the parking brake is not fully released, possibly due to a rusty cable, (can you say "Wisconsin winter road salt")? This will prevent the auto adjusting system from operating.
Try these things, then holler back.
Saturday, March 28th, 2009 AT 2:51 AM