Could a Vacuum leak on a Brake Booster of a 1972 240z be the cause for rough idle and stalling at traffic lights or intersections after 15 mins of driving? Mechanic carried out a test with a mechanical pressure pump and the booster did not hold the pressure. Just trying to find common sense before wasting money on a brake booster

 

If the brake booster is leaking, it needs to be replaced... but first you should rule out the inline check valve. And have the brakes always felt squishy? Have to press hard on the brake pedal?

The part that doesn't make sense is why it would start after 15 minutes... a vacuum leak is a vacuum leak. If it were entirely related to a leaking brake booster, wouldn't it have problems every time you apply the brakes?

 

How do i rule this out??

 

Well the check valve is just a one way ball check valve... only allows air to move one way, stays closed the other way.

Seems like you had carb problems last year... did you get them sync'd / tuned?

 

Carbs are synced! Problem is that whenever the car is stuck in traffic after 15 mins of driving the idle becomes rough and the plugs start to become black till point where the car stalls. How do i rule out the brake booster does not have a vacuum leak? The pertronix coil does get very hot!