I have a 2005 Ford Taurus that I am having brake problems with. On a long trip the front brakes suddenly stopped working. The pedal went all the way to the floor before the back brakes would finally stop the car. We bled the brakes and changed the Master Cylinder but it still didn't work. Took it to a mechanic and he bled the brakes again. It worked for about 30 miles but then stopped again. After letting it sit for two days it seems to be working right for the most part but the pedal is still slightly squishy and they went to the floor once, pumped them and it immediately started working again. Everyone I know is stumped, including the mechanic, so I'm wondering if there is anyone who knows what could be causing this to happen? If it makes a difference there is also a constant high pitched squeal coming from the right front tire when going down the road and the brakes started squealing again when stopping, shoes pads and rotors are new though.
Why would brakes fail then seem to come back after changing the Master Cylinder but occasionally not work?
They need to be bled agin, but RIGHT this time. Do you know if the master cylinder was bench-bled? If not, that is the problem. The reason the pedal keeps going from firm to squishy is because there is air in the system.
There is still air in the system somewhere. they may have to bleed all 4 bakes to get it all out. or at the proportioning valve. does the brake light come on?
Why would brakes fail then seem to come back after changing the Master Cylinder but occasionally not work?
did you get a new master cylinder? I have had bad ones right out of the box before. Rebuilts are not very reliable. The inconsistent braking could be a bypass in the master cylinder. Which means it is leaking internally. If the pedal is squishy, it probably isn't bled out well enough. Sit in the car and start it up, leave it in park and push on the brake pedal once and note how low it goes before it bottoms. Then VERY VERY VERY VERY slowly push down on the brake pedal and see how far down it goes. It will go even lower if it is bypassing. Repeat both steps and compare. If it is the same or higher, then it needs to be bled out very thoroughly. Maybe with a vacuum bleeder if he didn't bleed it before installing.
Check the brake proportioning valve. They can sometimes get air trapped in them if the master cylinder is not bled properly
I would check the vacuum canister, And the brake relay on a ford. Don't know what they call it but it cost.
