Hissing and sticking brakes - bad Booster?

[Bill.Oakes]

Thought I'd better change threads for this one:

I've been bleeding them like crazy with no results, but now have read more on the site about the booster and fear that might be it.

There is a lot of hissing when I pump the brakes, lose all pressure when I start the car and the pedal sticks pretty bad on the way back up from stepping on it. I disconnected the pedal to make sure it wasn't the pedal itself, definitely coming from the rod that attaches to the pedal (and the booster).

Damn, I have a race in 6 days, is there a solid test to prove that it's the booster, not air?

thanks

-Bill

[sblake01]

If you have access to a vacuum pump, connect it to the inlet on the booster and see if it holds. If it doesn't it's bad.

[Bambikiller240]

Could the "Check valve" in the line to the Master Vac be installed backwards?

[Bill.Oakes]

Having some debate with a neighbor as to which way the check valve should go - should it let vacuum go into the booster or out. Or maybe better to put it, which way should the air flow, toward the engine or away from the engine?

By the way, I did replace the booster with a newly rebuilt one. The pedal is much smoother (the old one hung up about half way back up) and no hissing now.

Still no brake pressure unless I pump it several times, but I fear it's the air bubble demons at work, isn't it?

[2ManyZs]

Check valve should have an arrow on it, it goes into the firewall bracket with the arrow pointed towards the Master-Vac.

[Bambikiller240]

Originally posted by Bill.Oakes

Having some debate with a neighbor as to which way the check valve should go - should it let vacuum go into the booster or out. Or maybe better to put it, which way should the air flow, toward the engine or away from the engine?

The Master Vac "stores" Vacuum (low) pressure that was "created" by the engine operation for use as needed to operate the brake system. Thus air flow must be "towards" the engine (out of the Master Vac).

[ChrisA]

Hi Guys, when the booster on my 72 failed, you could hear vacumn leaking into the drivers compartment at the rod when you stepped on the pedal. And the pedal movement was really stiff. Made the engine stumble when you put your foot on the pedal even the slightest. I got a booster off a 76 280Z at the bone yard but the four mounting studs are set in a bigger square pattern than the 72. Since my 72 is a rusty daily driver I drilled new holes in the firewall and mounted her up. Works good so far. I was told by a local brake supplier that there are no more of the older boosters available. Except from VB and maybe Motorsport. Anyone out there try a rebuild kit in theirs?

FWIW

Chris