i am runing 120y disks and stanza booster and master cylender. My problem is that my brakes are hard as a rock as if the booster is not working. I have had the booster checked out and it is working fine and the vacume line that goes to the manifold is not leaking i tried a diferent booster and even though it was leaking it still boosted beter than the one i had checked out untill you hit the brakes hard then they went hard
wat could be the problem?

do you have the one way valve installed? The booster only needs vacuum, if you had a turbo you'd have really hard brakes under boost. I reckon you are missing the one way valve between the booster and the manifold.

if you mean the one on the vacume line for the booster yes i do, unless it is not working

yeah..it's possible it'll be stuck open.

pull it out and blow and suck through it, to see if it works. Soak the one way valve in some kero for a while, it should free up.

i just went out and checked it out and it seams to be working freely it has got me stumped

ok then. It almost certainly has to be the booster.


Do you have trouble setting the idle? If you do, you could have a hole in the booster diaphram

Can you blow back into the manifold? could that hose be blocked?

oh yeah..is the one way valve installed the correct way around...with the flow going towards the engine?

i wold not have thaught that it would be the booster (allthough it is pointing in that direction) as i have had it checked by the profesionals and it came back ok. It idles fine with my foot on or off the brake
and the vacume hose is brand new.
One thing i think is weird is that wen i disconect any of the vacume lines it actualy idels faster

I now reckon the valve is installed backwards. I hope I'm right. If you remove any vaccuum hoses, you need to block them. Otherwise you are getting more air that isn't metered through the carbie or MAFM, depending on what you have.

the one way valve only goes one way the end that the hose joins to is smaller than the end that goes in to the booster