Power Brake Booster bad?

[Pat Bush]

Hello all -

Seem to be having some intermittent problems with the brakes on my 1970 coupe. This is a power brake car. Usually when I take the car out the brake pedal goes to the floor until she warms up (unless I pump it several times). The car always stops though. After it warms up, the car stops fine and the power assist seems to be working. Sometimes when I push down on the pedal I can hear it hiss as it goes down to the floor. I just had the master cylinder replaced, and the car has less than 500 miles since an engine compartment restoration with new front calipers.

Would this be indicative of the booster or check valve (or both being bad). I am thinking the chances of two master cylinders being bad is pretty thin especially since it always stops.

Thanks in advance --

Pat

[Jim T.]

Re: Power Brake Booster bad?

I have a 70 with power brakes and this has not happened yet with the original power brake booster. However with my 85, it happened about 5-6 years ago. Just like your 70, when I would push down on the brake pedal I would hear the hissing. I went to Auto Zone and bought a new replacement power brake booster unit that was guaranteed for the life of the car and it cost a lot less than what GM wanted. The unit from Auto Zone was just like the original equipment made by the same company.

[Jim T.]

Re: Power Brake Booster bad?

Just read your profile, with that LS6 you need some good brakes. Your 70 with power brakes should have a very full pedal with your new master cylinder and installing another power brake booster. If you want to retain the original I think there is an advertiser in the Driveline that rebuilds these power brake units.