Stalls when braking

[Lorinm]

I have a 1996 Buick roadmaster- was running fine then it kept stalling when I touch the brakes - replaced all Vacum lines - replaced the check valve on the brake power booster - ideal fine - can get it up to high ideal - then push on brakes it stalls

 

[HotZ28]

It sounds like the diaphragm in the booster is blown & leaking? Can you put a vacuum gauge on the engine to see what the vacuum reading when it is idling, then press the brake to see what you have?

 

[Lorinm]

It sounds like the diaphragm in the booster is blown & leaking? Can you put a vacuum gauge on the engine to see what the vacuum reading when it is idling, then press the brake to see what you have?

Thank you - I had a mechanic look at it he did a pressure test said it’s fine and holding - he is com8ng back Monday to look and see if he can find the problem- any suggestions would be appreciated

 

[DrivenDaily]

When the brake is pressed, it opens one valve to disconnect the two sides and then admit ambient pressure into the chamber toward the driver.

Summit Racing has a simple diagram on how it works at this link.

If the 2 chambers are not isolated while ambient pressure is filling the "back" chamber, then it'll also enter the "front" chamber that should always have vacuum.

THIS is what would indicate that the booster may need serviced or replaced.