snafu7x7

I had the brakes completely fail about 4 months ago, it was scary because they started to feel a little 'mushy' (no resistance on the pedal until it got near the bottom) but they still braked fine, then they just failed completely.

I took it in and had them inspect the entire system, they checked the front and rear for signs of wear and found they were in good shape (makes sense, I had them replaced 2 yrs before that). But the master cylinder was bad. So they replaced that, filled it up with fluid and checked the whole the system for leaks and it all looked good. It drove fine for the first little while, lots of resistance on the pedal, good braking all around. But now it's going mushy again (braking only when the pedal gets near the floor). I checked the fluid level and it is near the top (maybe a 1/8 inch below the top which seems fine?). What could be going on here, do I have a lemon of a master cylinder maybe?

Richard1916

if your car has disk front brakes it could be the factory proportioning valve failing,if it has one .if yours is 4 wheel drum make sure shoes are adjusted right if they are too far from drums on all 4 corners the springs will slowly pull the shoes away from drum and it will take a lot of pedal travel to take up the slack before the shoes start touching drums.
the old school guys adjust shoes with wheels still on by tightening until when you spin wheel by hand it will stop turning between 1 and 2 rotations.

69mach1377

I vote for a bad MC...any signs of leakage near/inside the fire wall?

bop11

You probably have power brakes on this and your Booster could be bad. It should have been replaced when the master cylinder was replaced. Also check the vacuum lines to the booster are not all cracked or lose.

Mach428

I would take it back to whomever did the work. The way you've explained the problem, it sounds hydraulic to me rather than mechanical (adjustment.)

If your car has power brakes, you didn't mention if the feel of the brake pedal changes between engine running and engine off. I would check to make sure the PB unit is sound.

If you do replace the PB unit, I would definately buy one with a master cylinder installed. It's not worth the headache of trying to get one to work with the other.

snafu7x7

OK I got an update to this. I took it back to the shop and the best they could determine was that it was a failed Master Cylinder (brand new part failure...it happens) so they replaced it and I was good to go for awhile.

Just recently though, it's run into a different problem. Now the brake pedal isn't mushy at all, it's the opposite, its become really hard to push down on and you really have to come on to it to brake. It feels like there I've lost power brakes or something. Any idea what might be going on now?

bop11

Either vacuum leak or a bad booster, or the connection between the master and booster. Take Mach428 advice and get a system that is made for each other.

snafu7x7

Is there an easy way to test for that? I double checked the vacuum hose just in case it was not secured properly or split and it appears ok. The booster is probably original so it wouldn't surprise me if that was the problem, but I bet it's a bitch to replace?

Mustangdemon67

when installing a new master it needs to bench bled before the install. sadly many shops dont do this and you ll never get all the air out of the system no matter how much bleeding you do. this may be the problem. usually when a booster goes bad you ll hear hissing but boosters are just brake assist so a little lady can stop as hard as a line backer.

Mustangdemon67

could be a few different things here. do you have drum all around?

im thinking that because of your soft pedal the shop adjusted your shoes out much more to compensate and your probably getting major drag. also causing the harder than normal pedal.