[Whittaker]

My new master cylinder was bench bled then when on the power booster it only pushes fluid at the very end of the throw of the pedal. Which for power brakes with no vacuum I figured was OK. But it doesn't want to bleed the brakes. The booster is a stock GM that was in working order the master cylinder is a new Bendix or ? for a 70 Corvette. So what gives. I can get fluid at the calipers using my vacuum pump but nothing when the pedal is pushed. Do I need to adjust something between the booster and MC or the rod into the booster?

OR?

 

[Schurkey]

drum brakes on the rear of the car? If so, the 'Vette master cylinder won't work properly. It has no residual pressure valve.

Are the rear brakes connected to the rear of the master, and the fronts to the front? If so, first guess is that the pedal has to pressurize the rear wheel cylinders before the front piston even moves. Hence, no fluid output for the front brakes until the pedal is WAY down.

 

[Whittaker]

It will have discs in the rear. I have an adjustable prop valve in there. So unless I do the rears the fronts won't bleed? I'm waiting on my 12 bolt to be done so I can put it in with the discs then bleed them. I was trying to get the fronts so I had brakes to roll it around with. Its not running yet.

 

[von]

Do you still have the old MC to compare with? I think there are different depths in the main piston for the rod on the booster to fit into. Be sure your MC has the correct depth for that booster rod.

 

[Schurkey]

von has a good point. Worth checking.

If I'm right, you could swap the front brake tube to the rear port of the master, and at least the front brakes would work. Putting the rear brakes on the front of the master shouldn't cause them to work worse than they are now.

 

[Whittaker]

The old MC was manual/ non power single cylinder. Don't think it will help.

 

[soccerguy045]

Just to throw this in, we tried this on my chevelle, but put the calipers on upside-down/wrong wheel. Air has to bleed up. Unsure if that helps...

 

[Whittaker]

The pedal feels like it catches on something about 3/4 the way down then it seems OK. But it still doesn't seem to push the fluid.