1991 Camaro RS LO3
Disc/drum stock setup
Rotors, calipers, brake pads, drums, rear shoes, etc. all fairly new and checked out ok by shop (Midas?) yesterday. They said the brake lines were ok. No lines leaking. Reservoir full.
The problem happened all of a sudden coming home from work.

Here are the symptoms:
Start car leave house hit brakes 1st time no problem. Let off brake pedal drive 10 yards.
Hit brakes the 2nd time, harder to depress brake pedal and less stopping power. Let off brake pedal drive 10 yards.
Hit brakes the 3rd time, even harder to depress brake pedal and hardly any brakes.

Let off brake pedal, drive for short distance, hit brakes everything seem ok. Repeat above.
Brakes in a straight line. Does not pull one way or the other.

In other words if you feather the brakes, it is like I lose vacuum. If you continue to drive a short distance id 50 yards or so, the vacuum recovers.

I installed a new power brake booster even though I did not think that was the problem. The problem is still there.
Rubber line from check valve on power booster to filter ok.

I'm out of ideas. I guess I will have a shop power bleed the system and put in new brake fluid.
Could it be one of the front caliper pistons sticking? Rubber brake lines collapsing?

Thanks!!!

 

Easyest way to check your vacuum assist brakes is to start your car and let it idle to build up vacuum. Wait about five mins and then hit the brakes. You should get 4 or 5 assisted pumps if your not losing vaccum. Then with the brake pumped up press on it and start your car. If the pedal drops your diaphram is still working correctly.