[williaty]

Alright, so I have almost NO brakes whatsoever. Honestly, the parking brake at half-tension is worth more than the main brakes right now. I have no idea what's going on, but here's what I do know:

The front suspension and driveline were completely removed from the car to facilitate a variety of mods. At one point, I had to start the car to check on a mod I had just completed. Out of habit, I pressed on both the clutch and brake to start the car. Sadly, the right front caliper was hanging (empty) from the spring at that point. So the pistons moved all the way to the fully extended position. I left it like that for 24 hours while the rest of the car was rebuilt. The pistons did not come out of the caliper and were pressed back to the fully retracted position with a C-Clamp and installed onto the rotor. There was no weeping fluid evident anywhere.

Upon starting the car and rolling it out of the garage, the pedal went to the floor. I mean it crashed right down all the way. It just barely had any detectable spring against my foot. It make a thunk when it ran into the firewall. Turning the engine off, it took 4-5 full pumps to bring up any pressure, but the pedal did not sink once pressure had been built. This immediately screamed "air bubble" to me. So I bought a liter of fluid and bled it through the brakes. Not a single damned air bubble came out.

After talking with an expert, I cycled the ABS about 4 times. This did result in the pedal becoming firm when off, but it still goes straight to the floor when the car is running. So, here's what I've done so far:

1) Bled a crap load of fluid through the system.
2) Cycled the ABS 4-5 times
3) Bled even more fluid through the system
4) Cycled the ABS another 3-4 times
5) Bled the system again, this time with the engine running (just to see if it made any difference)
6) Verified there's no fluid leaking at any of the pistons, bleed valves, or lines
7) Verified that there is no vacuum leak at the Master Cylinder


Here are the current symptoms:
1) The pedal is high and hard from the 1st press with the car off
2) With the car off, the pedal will not since towards the floor if you keep pressure on it
3) As soon as the car is started, the pedal sinks to the floor with minimal effort. I literally think I could set a can of pop on it and it would put the pedal against the firewall
4) Something makes a wooshy pneumatic/hydraulic noise when the pedal is depressed. For all I know, this may be normal.

Any guesses?

[SAx COLIN STi]

Do you know if the master cylinder ever ran dry at any point? If so, you could've lost the master cylinder seals. Might have to replace it. Happened to me once on a Toyota Land Cruiser

Before replacing the master you could also try bench bleeding it out of the car.