Brake pedal travels to floor with engine on
 

I am at a loss of what is going on with this vehicle. It is a 1999 Camry, 4 cylinder with ABS. I was helping a friend change the pads and shoes on his car. After replacing the pads and shoes which went really good the problem started. It seems to have started when the bleeder screw on the passenger front caliper twisted off leaving the threaded part of the bleeder screw in the caliper. I decided to replace the caliper and replaced the driver side at the same time. After replacing the calipers I bled the entire system. All air was removed but the brake pedal traveled to the floor. Talking with a mechanic friend he said it sounded like the master cylinder went bad. So I changed it and made sure to bench bled it before installing. I bled the whole system again including the brake line connections at the master cylinder. The problem still persists. Here is where I am at a loss; other than the pedal going to the floor the system works fine. I have driven the car down the road and slammed on the brakes doing about 30 mph it stops quickly within 20 feet or less. The pedal does not need to be pumped to build pressure. It even engages the ABS and it feels like it is working fine. I took it onto some dirt roads to make sure the ABS was definitely working fine and it seems to engage and stop like it should. After getting it back to the house I re-bled the entire system again including the fittings at the ABS actuator and the proportioning valve to make sure that no air was trapped. Then I pulled off the vacuum hose from the booster with the engine running and had my friend step on the brake pedal. The pedal is firm like it should be. Once the vacuum line is reattached the pedal drops to the floor. From reading the forums I don’t think it is the booster since a bad booster means the pedal is hard to push, or is it the booster? This was my next step unless there is something I am missing. Any help in figuring this out is appreciated.

Travis

To check the booster operation:

With engine on press brake pedal a number of times and watch pedal travel. Pedal travel should not increase (the pedal becoming closer to the floor with each additional push).

Assuming it passes this test, depress brake pedal and start engine. Pedal should drop slightly and then hold.

To check for vacuum leaks:

Run engine for a few minutes then slowly push on the pedal a few times. The pedal should drop the farthest with the first push then gradually rise with each additional push.

With engine running push on pedal and hold foot pressure while turning engine off. Hold pressure on pedal for 30 seconds and watch pedal travel. Pedal should not start dropping.

As the other issue. Toyota does not have any special procedures for bleeding the ABS system. Start with bleeding the master cylinder then move to each brake line.

Sometimes bleeding the master cylinder can be a pain. Might disconnect the lines then with reservoir full press slowly on pedal. Before releasing have someone block off the now open ports on the cylinder body with their fingers. Repeat this process 4 to 5 times. Of course make sure you have something to catch the fluid coming out of the ports.

Then bleed the lines.

Thank you for the help in the direction to take. I will check these out next week as it is my friends car and he is out of town right now.

Wanted to follow-up with what was the cause of this problem. The master cylinder was taken apart to verify the seals hadn't moved and they hadn't, they were just fine. Didn't think it was the brake booster just by indications. That led to just changing the proportioning valve and that seemed to fix it. Not sure why that was the issue but it worked. Hope this helps others if they are having the same issue.

Thanks for posting back with the find.