I have a 1993 Buick Lesebre. My ABS brakes have failed 3 times in the last 12 monthes at a rate of about once every 3 months. Pedal goes to the floor, pumping does not restore pedal, ABS trys to work ( slight ABS noise ). After about 5-10 seconds, the last pump seems to work and brakes return to normal. Fluid level is full. Once I was stopped at a stop light with foot on the brake. Pedal goes to floor and after a few seconds brakes go back to normal. The other two times I was going about 5 MPH. Master cylinder was replaced about 12-14 months ago and leaking wheel cylinder replaced. Any ideas? Nobody up here has a clue.

[QUOTE=kefgene]Once I was stopped at a stop light with foot on the brake. Pedal goes to floor and after a few seconds brakes go back to normal.


Sounds like your new master cylinder is defective...... It doesnt have to be leaking to be defective. It is bypassing.( fliud going back into resivior instead of holding pressure).

the fitting connecting the vacuum hose to the booster is a check valve. however remote the possibilty may be, it could be defective or contaminated. you might consider changing it out.