I've got a scary intermittent brake problem. Sometimes when I get on the brakes fairly hard(more than a normal stop, but not enough to lock the wheels on a dry road) my pedal goes limp, and the brakes stop working. It feels similiar to locking the wheels in the snow, but I know they not locking up. If I pump the pedal and the brakes come back. It's happened 4 times, and I'm afraid I won't be so lucky avoiding an accident next time. I really need some help with this one. I was thinking it was maybe a booster issue, so I checked the PS fluid level, and it's full. I don't have front ABS, and no warning lights come on after, or during it happens. It's only happened with the wheels straight, not trying to go around a turn, but the power steering still works. I had to swerve around a car once and had no trouble turning the wheel.

 

This will test out the Booster System:
Brake Booster

With the transmission in NEUTRAL and the engine stopped, apply the brakes several times to exhaust the vacuum in the vacuum boost system or the pressure in the Hydro-Boost system.

Hold the brake pedal in the applied position.

Start the engine.

If the power brake system is functioning properly, the brake pedal can be felt to move downward after the engine starts.

With a vacuum type power brake booster, if engine vacuum is available to the power brake booster and no power assist is felt, replace the power brake booster and retest the system.

If power steering pump pressure is available to the Hydro-Boost power brake booster and no power assist is felt, replace the Hydro-Boost power brake booster and retest the system.

If power steering pump pressure is not available at the Hydro-Boost power brake booster, check the power steering pump pressure and flow.

Accumulator, Hydro-Boost Only

Start and run the engine.

Stop the engine.

Apply the brakes. The accumulator in the Hydro-Boost power brake booster should retain enough pressure for at least two power assisted brake operations. If no power assist is felt, replace the Hydro-Boost power brake booster and retest the system.