At random my brake booster will have positive pressure and the pedal is rock hard no more assist. When I take the line off there is a burst of air. The check valve inline is working but because of this problem it leads me to believe it's on it's way out. Can I just use a 1 way check valve from say JEGS and use AN fittings/hose or should I just buy an OEM one? Or is something else wrong?

 

Whats on its way out? The valve or the booster? The valve is a simple check valve, any replacement valve will work(does not need to be OE) Turn the car off and pump the brake pedal. A good booster will have about 3 or 4 pumps after the car is off. This shows its holding vacuum.

 

The pedal only gets stiff after hitting the brakes 2 or 3 times with the car off. Seems perfectly normal. But for some reason at random while driving the pressure doesn't release out of the booster or vacuum doesn't suck through to have an assist. While the car is on rapidly pressing the pedal the idle isn't erratic or anything which leads me to believe the booster is fine but the check valve in the hose is not.

 

Booster must be trashed and those symptoms were it just on it's way out. Plenty of vacuum but no assist at all now. Rock hard pedal, still stops but if it weren't for me having strong legs stopping would be impossible. I wonder why a 2 year old booster would fail though? The master cylinder isn't leaking at all.