Brake Booster Hiss

[Gambit]

the port on the one way valve you blocked, i think that is still needed to balance the one way valve - otherwise if it was true one way there would be no need for any vacuum connectors at all on it.

you could try and block both ports and see do you still get the hissing.

 

[Coog]

Both ports (the blocked one and the one going to the dizzy) are before the valve and on the same stretch of pipe. The valve only appears to serve the booster if that makes sense. I'll try blocking it to see what happens.

 

[NoGrip]

My guess is the vacuum valve in the servo is at fault. The rubber diaphragm must be okay if you are getting brake assistance. The one-way valve from the inlet manifold must be working if it’s holding vacuum once the engine is stopped. The servo units are easy enough to disassemble & rebuild.

 

[Coog]

New servo arrived today. Will take the old one apart on the bench and see if there's anything I can do with it and then potentially shift it on.

Thanks for the tips and advice

 

[Coog]

Yeah that's probably the fault there. That might be rebuild-able in future but I haven't the time / patience for it now so the new one went in and we have pedal again and no mad air noises so finally happy with the brakes.