280Z Bad Brake Booster?

[Indey]

I have a 76 280Z, and today when I went to move it into the garage, the brake pedal basically sunk to the floor, and only the very last bit of pedal space, would allow the brakes to be used....very slightly . I checked for leaks everywhere, and I have yet to find one. There is fluid in both reservoirs of the master cylinder, and it is a brand new master cylinder.

I also tried pumping the brakes with the car off to see if the pedal would build pressure, and it did not, it would just continue to pump and never stiffen up.

So does this sound like a bad brake booster?

[pwd]

No, not a bad booster, it's just there to reduce the effort a little. If you're not losing any fluid to external leaks, then you have a problem with the Master Cylinder itself.

[Indey]

No, not a bad booster, it's just there to reduce the effort a little. If you're not losing any fluid to external leaks, then you have a problem with the Master Cylinder itself.

that would be very annoying considering it's a new master cyl..

[Jeff G 78]

New (rebuilt) MCs are know to fail due to poor quality. Check for leaks, but it sounds like there was a rough spot in the bore and the seal got knicked.

[Indey]

Alright so upon further inspection, since I only had a few minutes before to check the ground/engine compartment for brake fluid. I do have a leak at the drivers side rear wheel cylinder.

The front brake reservoir was full, and the rear empty.(to which when I had checked earlier looked full, but I suppose I should have just removed the stupid cap ) I removed the master cylinder just incase some had gotten by, and nothing was leaking from the master cylinder still.

I refilled the master and bled the brakes, but I still have no pressure at all, and if I bring the brake pedal all the way to the floor it will kind of brake, a bit. Also when I do so the brake light will come on. So basically the only way for me to scoot it around the driveway is to rely on my hand brake.

Could that rear cylinder allow so much fluid out that the brakes would have no pressure at all?

Edited September 14, 2010 by Indey

[sblake01]

Did you bleed them in the right order? (LR-RR-RF-LF) You could lose your brake pressure if the wheel cylinder leak is bad enough.

[Jeff G 78]

Sounds to me like you need to bleed the master. Install a 6" hose on the bleed port and put the other end in the reservoir below the fluid level. Open the bleeder just enough to get flow and slowly pump the pedal up and down until no bubbles appear. Tighten the bleeder and repeat for the other port. After that is done, try bleeding the corners in the order Mr. Blakeney described above. If the LR won't bleed, the cylinder is likely shot and needs a rebuild. If the bore looks good, buy a $5 rebuild kit. If not, get the whole wheel cylinder. Luckily, you have a '76 and they are cheap. The older ones are getting expensive and hard to find.