poor brakes

[37fordpu]

Hi guys I just set up my brakes on my pickup and bled them . I have a firm pedal but the brakes a crap. I used a 1 inch commodore master onto a 1992 fairlane dual diaphram booster. I had the booster rebuilt. EB ford rear calipers and Vt front calipers. I have the car on stands and with it running in gear I have to push very hard to stop the rear from turning. Any ideas where to start looking would be appreciated.

[Gojeep]

So with the engine running they still feel rock hard? Does the pedal move much in it's travel?

[37fordpu]

Hard pedal but engine nearly stalls so I am thinking there is a vacuum leak inside the booster . I will take it back to the repairer to get it checked out

[hudson nut]

A smaller bore master cylinder will require less foot effort at the pedal. When I bought the masters for my current build, the Willwood technical department helped me figure out what the bore of my masters needed to be, to work properly with the calipers I am using. I had to tell them how many pistons per caliper, and the piston bore size. They did the rest.

Dany

[Harv]

Could be a vacuum leak, but the would need to be a pretty big one to stall an engine. When the booster leaks vacuum, the engine gets a little bit more air, and the revs normally increase slightly. It's normally only slight as the vacuum line is normally plumbed in downstream of the carb... you don't get any more fuel, just a bit more air so the mixture leans a little. It would need a big air leak to lean the engine out to stall.

Cheers,
Harv

[Sudsy]

Easy enough to test the booster. Run the engine. Switch off. Remove vacuum line from booster with the fitting. It should be difficult to remove and then you will hear it suck air if booster is good

[Gojeep]

Also make sure you are using popper vacuum hose and not fuel hose etc as it will collapse otherwise. Also have a large intake manifold port for the supply.

[zuffen]

I think we need more information on what the system is made up of.

Is it all disc, or disc/drum? Does it have a proportioning valve? If so is the valve for a disc/disc or disc/drum arrangement.

I know my yellow pickup has very little braking effort on the rear and it doesn't have a proportioning valve. Never solved it and probably never will.

Does the pedal go hard on the first push or on subsequent pushes?

Rock hard pedal and little stopping power suggests no boost or poor ratio of master to wheel cylinders, or pedal ratio.

[37fordpu]

I had the guy that did the booster up look at it and turns out that a circlip in the booster had dislodged on the diaphragm push rod side allowing a seal to leak all good now thanks for all the advice.

[Gojeep]

Glad it was an easy fix.