Replaced master cylinder, now NO brake pressure, what's wrong?

Question

I own a 1993 Pontiac Grand Prix.

My brakes were weak and a professional inspection diagnosed the problem as master cylinder failure.

I bought one from autozone and took it to a shop, who put in the part and did a brake fluid flush and replacement, but now there is NO brake pressure at all, and they are telling me I might need to, replace the ABS pump... but I can't see how I would not have regular brakes if the ABS wasn't working- especially because the brakes were working a little before and not at all now.

What could be wrong that the shop isn't noticing.

Thanks for your help!

Answer 1

is the brake fluid going low? if its not never rule out defective parts i bought a "new" master cylinder from autozone and it turns out that the part was messed up i thought it was something else like the abs but it wasnt try taking the car to someone else to get a second opinion.

Answer 2

The prob. here is you told the shop what you wanted done(brought them a part and said install) if they had made the original diagnosis you could demand more from them. but in this case I'm afraid you set your own trap by wanting to save $ on the part price..or it is possible that they did not bleed the system properly. I would go to diff. shop now for new diagnosis. It cost too much to keep guessing plus if you rear end someone -big  problem..good luck!  Real professional break shop doesnt have to guess.

Answer 3

power brake booster.may b bad,,,also bleed it again...the ABS is a separate electronic sensor/computer system...i disconnected mine because it was going through sensors 2 @ 125 dollars each...No ABS and my brakes work fine. and the other guy is right...you can get new/rebuilt parts that don't work...try pulling the ABS fuse...may b they are locking the calipers.

Answer 4

did you bench bleed the master cylinder before you installed it? you probably have air in the lines.

Answer 5

maybe the leak is somewhere else, like at a caliper or something.

there is nothing wrong with your brake booster and the people that say that there is really need to do some googling before giving out crappy opinions.

Answer 6

sounds like your shop is trying to pull a fast one over you .....you prime the new master and you then bleed the brake lines take about a good hour and abs could have something to do with it but i dont think so... so im wondering would this be the same  professional  who told you the master was bad and really if either was a real pro they would have tried to stop you from drive it with a bad one

Answer 7

check for bad lines.

Answer 8

Could be a brake booster, your booster gives the master cyclinder pressure, if not you got a bad master cyclinder.

Answer 9

Have them re bleed your brakes.They didn't get all the air out.