So my friend and I finally changed my front brake pads, rotors, and calipers yesterday. Everything seemed to go well and we bled the brakes until there were no more bubbles and new fluid came out, but when I started the car, the pedel felt really mushy. I had to press the pedel down to the floor to keep the car stopped even in idle. We figured air in the lines, so we did it again the same way - LR, RF, RR, LF. We pushed the brke pededl several times, kept it held down, opened the air bleader valve to let air into the bleader kit, closed it, and the released the pedel. We did several times for each wheel, but there was no air - only new fluid. We've done the whole bleeding procedure about 5 times now, and there is no air we can see coming out of the lines.

What's going on? There are no leaks either. The only strange thing (I think) is that is when pulled the vaccum tube that runs from the brake booster to the valve the brake pedel feels normal. We replaced the valve thinking it was bad, but when we replaced it with a good one there was no change in the brake pedel feel.

Neither of ius have any ideas what it could be. The brakes were working fine before. I used Castrol brake fluid which says it exceeds DOT3 and DOT4 specs, Raybstos quiet stop pads, pro stop rotors, and pro stop calipers.

 

When you pull the vacuum hose off the brake booster basically you have manual brakes at that point. The pedal will feel harder but you have no power assist, for obvious reasons. One thing I use to tell my customers when doing a brake job that requires bleeding, is that there's a possibility that the master cylinder "might" go out during the bleeding process depending on the mileage and condition of the master cylinder. When you're bleeding the air try not to let the brake pedal go all the way down to the floor when the person opens the bleeder screw. By letting the brake pedal go it's full travel there's a possibility the piston seals in the master cylinder might get damage. It's kinda like when you have a frozen caliper or a brake hose that collapse internally, you can't really explain why it happens it just does. If you're convinced you did the bleeding process correctly you might have a bad master cylinder.

 

is there a way to test the master cylinder to see if it's bad?

 

Not that I know of, besides hooking up pressure gauges at each wheel. But at that point you might as well buy a master cylinder and try it out. My advise try bleeding the system one more time from RR, LR, RF, LF without allowing the brake pedal to go all the way down when opening the bleeder screw. The person who's opening the bleeder screw is controlling how far down the brake pedal will travel, depending on the time length he has the bleeder screw open. If that still doesn't help, and no one has any other suggestion you're left with my suggestion.

 

Thanks Candiman. I'm going to take the car (slowly) to the shop and have then bleed it with their machine. That should guarentee no air in the lines.

 

Please let me know what came of this as I have the very same problem.