What are the signs of a failing master cylinder?

[woodyjeep]

ok, so I did some testing. I found that if I squeeze the back brake line to where there is little to no flow the brake pedal becomes firmer. If I do the same to the front left caliper (the one I changed) the pedal becomes firmer. If I do it to the front right caliper nothing changes. So this leads me to believe I have to fix my back brakes and my front left caliper. Anyone agree with me?

 

[xjbubba]

When you say the pedal becomes firmer, do you mean it feels normal, or almost normal? If it feels normal, then you need to address the rear brakes first. Poorly adjusted rear brakes can cause low pedal. You previously stated partially applying the E-brake improved pedal feel. Probably because applying the E-brake moved the brake shoes closer to the drums. This would tell me that at a minimum you need to adjust the rear brakes. Did you inspect the rear pads, drums, and wheel cylinders? It's possible the whole rear system needs rebuilt.

Once you get the rear system squared away, go back to the front. Sounds like you either have air in the caliper you just replaced, or possibly misaligned pads, or loose wheel bearings. Insure the pads are parallel to the rotors, and there is no looseness felt while trying to twist the tire when that tire is off the ground.

 

[Johnny V]

> Once you get the rear system squared away, go back to the front.

Yep great advice! I spun my wheels, so to speak, and got nowhere with bleeding the brakes until I did an autopsy on my back brakes...I just looked at them prior.

 

[woodyjeep]

When you say the pedal becomes firmer, do you mean it feels normal, or almost normal? If it feels normal, then you need to address the rear brakes first. Poorly adjusted rear brakes can cause low pedal. You previously stated partially applying the E-brake improved pedal feel. Probably because applying the E-brake moved the brake shoes closer to the drums. This would tell me that at a minimum you need to adjust the rear brakes. Did you inspect the rear pads, drums, and wheel cylinders? It's possible the whole rear system needs rebuilt.

Once you get the rear system squared away, go back to the front. Sounds like you either have air in the caliper you just replaced, or possibly misaligned pads, or loose wheel bearings. Insure the pads are parallel to the rotors, and there is no looseness felt while trying to twist the tire when that tire is off the ground.

well the pedal did not feel like a normal pedal still. It got firmer at the end of the travel, so I wasn't able to totally floor it. I know I gotta rebuild the back brakes, do they sell kits for that? As for the front caliper the pads are wearing at an angle, so one side of the pad has more wear than the other.

 

[xjbubba]

Yes, you can buy re-build kits for the rear wheel cylinders; however, I think you'd be smart to just buy new cylinders. I don't think they are that expensive. You could just check the cylinders for leaks, or "weeping" under the rubber boot on the end of the cylinder. Take a blunt, but thin object and carefully lift the outer boot and determine if there are signs of seepage. If yes, replace the cylinders. Take the drums to a brake shop and have then turned, and buy new shoes for the rear.

If the front pads are not parallel to the rotors, it may take more brake pedal movement to move the caliper pistons into contact with the rotor. After you get the rears rebuilt, go back to the fronts.

 

[87manche]

New wheel cylinders are about 12 bucks. I just did them.
New calipers are about $25.
If your pads are wearing uneven it sounds like the caliper slide bolts are stuck. Take the caliper off and see if you can get the slide bolts out. Check them for pitting and grease them with high-temp grease. You can buy a small package enough to do both for about $1 at the parts store.

 

[Johnny V]

Also hardware for rear brakes (springs and cables) is about $10.00 per side. Please buy...