Brakes Are Too Hard

[stykthyn]

ok heres the setup. 99 calipers up front and drums in the back. 95 master cylinder and 3-2 conversion. when I first installed it everything was gravy. Car then had an engine fire and sat for a while. Everything is now in running condition again but my brake pedal truly feels like I have to stand on it and jump up and down to get it to stop. Fluid level is good and there is no air in the system. Could the heat from the fire have killed my brake booster? Its the only thing I can think of that would cause this issue.

 

[mikestang63]

that was my guess or it burned up the piston in the MC?

 

[stykthyn]

Is the piston was bad the pedal would fall straight to the floor

 

[reldla1996]

Sounds like the booster. If you put your foot on the brake, and start the car, does the brake pedal move?

 

[jrichker]

Power brake booster test:
1.) Check engine vacuum you should have 14"-18" of vacuum at 625-750 RPM, 18"-21" vacuum at 1000 RPM.
2.) Vacuum checks good, start car and run engine up to 1000 RPM for 30 seconds.
3.) Cut off the engine and then press the brake pedal 3 times. It should get harder to press and travel less each time you press it. If it doesn't, then the brake booster is suspect.

 

[stykthyn]

Sounds like the booster. If you put your foot on the brake, and start the car, does the brake pedal move?

pedal movement is normal, just takes fred flinstone level effort to stop

Power brake booster test:
1.) Check engine vacuum you should have 14"-18" of vacuum at 625-750 RPM, 18"-21" vacuum at 1000 RPM.
2.) Vacuum checks good, start car and run engine up to 1000 RPM for 30 seconds.
3.) Cut off the engine and then press the brake pedal 3 times. It should get harder to press and travel less each time you press it. If it doesn't, then the brake booster is suspect.

will do. need to pick up another vacuum gauge and will report back. There is a slight idle fluctuation that I strongly suspect is a vacuum leak related to the brake booster.

 

[Mustang5L5]

My guess is rubber diaphragm in booster is toast.