weird brake problem, cant find anyone else who has it.

[Guest HALLOWEEN Z]

I've had something wrong with my brakes that should have been fixed long ago. First off it's a 75 280z with a master cylinder that has been replaced a few years ago and a power booster that is stock as far as I know. With no vacuum(engine off) the brakes feel like they should with no vacuum. Just like they would feel if you were coasting down the driveway with the car off.

 

However with the engine running they still work fine as far as getting me stopped and they will even lockup with hard braking. The braking starts at about the right time as I press the pedal. BUT the pedal will easily go all the way to the floor if I'm parked. It would if I was driving to but it will stop very fast. It's like I have great braking but theres little resistance on the pedal. It does spring back up fine but very easy to push.

 

The master cylinder seals I think are fine It's not like I have to pump the brakes just put pressure and the braking stays steady.

 

Is there anything that could be wrong with the booster to make this happen? I don't think theres any kind of adjustment but it seems it would have to be it. The pedal seems adjusted ok because like I said the braking starts about where you would want it to I don't have to push the pedal far.

 

thanks, nathan

[jhm]

Possibly air in the system? If so, that would definitely give you "mushy" brakes.

 

Have you recently bled all four corners? If not, give it a try and see if the situation improves.

[MONGO510]

Reaction disc problem?

[Guest HALLOWEEN Z]

Yes I've bled them a few times and doesn't seem to matter. I don't seem to have any air in the lines. What do you mean by reaction disc problem?

[datsun79z]

Halloweeen Z;

 

What you describe sounds very much like a reaction disc issue based on my personal experience. I could go into detail, however it has been covered before. Use the Search feature looking for "reaction disc". Keep us posted of your progress.

 

Mike