Diagnosing P/B Failure (early A)

[dibbons]

Connected a vacuum gauge/pump directly to the p/b reservoir on the inner fender. It would only pump up to 5" for some reason (first time I have ever checked it this way). I then attached the gauge to the hose that connects to the little tank and started the engine. When I pushed on the brake pedal I noticed a momentary change in idle speed and corresponding loss of a few inches on the gauge (maybe from 18" to 15"). Seriously considering changeover to dual master cylinder and aftermarket power booster. I already had the fsctory booster rebuilt once.

 

[65 Dartman]

My wagon came with the same setup you are using but decided I will use an 8 or 9 inch in diameter mid-60’s Mopar A body dual diaphragm booster with a new dual disc master cylinder.

 

[dibbons]

Update: Tested the vacuum cannister/reservoir tank a second time (now off the vehicle) and was able to pump out enough for a 17" reading (vs the 5" reading earlier). It took several hundred pumps which I guess indicate my pump tool is not in the greatest shape. The gauge held pretty steady.