Brake Job gone wrong.

[Emperor Allmon]

Had my breaks checked. Brake Check told me it was the master cylinder and front breaks needed replaces. I purchased new master cylinder and replaced the old one. It went fairly well. I bench bled the new master cylinder and had little trouble installing it ... BUT when I bleed the system nothing goes well first a broken bleeder screw on my passenger rear, I replaced the wheel cylinder. Then I bleed in the order recommended by my Chiltons. Passenger rear, Driver front, driver rear, passenger front. Things go well until I get to the driver rear. My buddy pumps the pedal, holds, I open the screw, Fluid, I close the screw, system pressure is crap. It is worse than before, almost no pressure on the system. I start again and the same problem. I try and skip the driver rear and move to the passenger from and I get the same problem. I can get some pressure back if I just bleed the passenger rear and driver front, but the driver rear and passenger front mess everyithing up. No when I drive it I get some pressure, the brakes are soggy and there is this "clump" when I press the pedal about halfway through my braking. I can feel it in the pedal and the pedal jumps to the floor. Any help is appreciated.

 

[CaptainKrunch]

Assuming everything is installed correctly I would just gravity bleed everything again.

CaptainKrunch

 

[Pailyn]

Just curious. Who did the brake check and why did you need the master cylinder at the first place? Are you absolutely sure that you needed new cylinder and brakes?

I'm a big skeptic of anything auto mechanics tells me unless I can verify for myself. If they do brake checks, ask for actually millimeters of rotors and pads using the calipers. I don't want eye estimates.. anyway... if you were knowledgeable enough to tackle the brake job yourself I would reckon that you know if it was truly bad or now.

Yeah... I would try to bleed it again. I have bought a long hose at a pet store and routed it all the way to the driver seat as I pump the brakes ... one man bleeding operation. At least you had a friend to help..

 

[w_tom]

Have done same. A hose from cylinder bleed screw into a glass jar. Then slowly pumping the brake petal, adding fluid to master cylinder (so that it never goes dry) until brake fluid is comes out clear. No need to close bleed screw if hose is inside a pool of used brake fluid inside that jar. Just press and release petal slowly. Also quickly identifies an air bubble.

Furthermore, I agree with 'suspicion' of bad master
cylinder. They just don't fail unless brake fluid was
contaminated. Sound more like a brake line is clogged - again contamination when someone refilled brake cylinder?

Sounds more like you now have air somewhere in the lines. Get hose that is flexible enough to remain stuck on that bleed screw. Use that jar so that you can discover when air bubbles appear.

 

[Emperor Allmon]

Have done same. A hose from cylinder bleed screw into a glass jar. Then slowly pumping the brake petal, adding fluid to master cylinder (so that it never goes dry) until brake fluid is comes out clear. No need to close bleed screw if hose is inside a pool of used brake fluid inside that jar. Just press and release petal slowly. Also quickly identifies an air bubble.

Furthermore, I agree with 'suspicion' of bad master
cylinder. They just don't fail unless brake fluid was
contaminated. Sound more like a brake line is clogged - again contamination when someone refilled brake cylinder?

Sounds more like you now have air somewhere in the lines. Get hose that is flexible enough to remain stuck on that bleed screw. Use that jar so that you can discover when air bubbles appear.

Thanks for all the help. The car has 185,000 miles on it. There was no pressure in the lines with the old master cylinder and bleeding did not help. It turns out one of my caliper mounts was siezed from any movement so that wasn't helping. After cleaning up that mess I went through the bleeding process again. I am able to get the pressure up and the brakes work great, but I still have a problem if I open the driver side rear bleeder screw. I lose all my system pressure. If I bleed all three other lines I get it back. Very wierd.