I,ve bench bled the master cyl on my 59 chevy truck.bled all for wheels an the pedal goes flat to the floor still.If i block the front dics at the master cyl and blee the rears the brakes are fine .If i block off the rears and bleed the front discs, the brakes work for a few times then the pedal goes to the floor, if i pump the pedal the brakes come back for a while.There is no fluid escaping from the front cylinders. Any ideas?

Brake line busted somewhere? Is the linkage to the master cylinder intact? Master cylinder might have been installed incorrectly.

I would keep bleeding. If there is not any brake fluid leaking, there must be air in the system. with the master cyl cap off, open one bleeder valve on the front and let it bleed for 10 mins. close and repeat with the rest. there must be an air bubble in the system! good luck

you need to check the internal leaks of brake master cylinder..it might be rubber inside worn out...

yes may need to bleed lines at master cylnder

If the car has drum brakes in the rear, Jack the rear up and have someone push the brake pedal hard and you try to turn the wheel. If you can turn it you need to adjust the rear shoes. They may be traveling out so far that the fluid level drops causing the pedal to go to the floor. You must adjust them with the drum on till you hear and feel the shoes rubbing against the drum. Hope this helps.

do you have a self bleeder kit? first off, you have to bleed the master cyl back into its self and the combination valve before you go to the wheels. when you do that, I think you will find that you have air in the lines. disconnect both brake lines from the master cyl and put the bleeder kit fittings on the master cyl, then put the rubber tubing with the kit on the fittings and submerge it in the brake reservoir. make sure its full. then pump the pedal until you get a hard pedal. if that is the case, reconnect the lines to the master, then have an assistant pump up the brake pedal with the engine off, and bleed the combination valve which should be connected to the master by steel tubing. pump it up, then hold it down, and crack the fittings loose, one at a time until the pedal goes about half way down, but do not release the brake pedal until the line is tight again, otherwise you will **** air in the lines. after you do all that, go to the farthest caliper or wheel cylynder from the master and bleed that with the same technique,and dont release the pedal until you close the bleeder screw. unless you have a major prob, this will work.

When you bleed the brakes are you starting with brake furthest from the master cylinder? Also was the master cylinder bench bled? If everything there is okay and you are not getting any air in fluid stream, you could try bleeding the brakes by having some one slowly pump the pedal till it is firm. Then have them let off open first bleeder valve and slowly depress to floor and hold there untol the valve is closed. repeat this at all bleeders. You may want to have car running to do this. Try this and let me know.

Did you bench bleed the master cyl. before installing it? then when you installed the new master, did you bleed all 4 points? If yes, then check all for points for leaking caliper/s and leaking wheel cylinder/s. If the van has ABS, check the valve body for a bleeder screw and see if air bleeds out of it. If you've checked everything twice and did everything right then your new master cyl. may be defective.

sounds like a bad diaphragm in your brake booster. listen for air while running at booster , disconnect vacuum hose depress pedal if it is good there should be a big difference in pedal

5 Inspect Brake Fluid Type Brake fluid loss or contamination 10 Inspect Master Cylinder (Brake System) Worn or leaking brake master cylinder. 11 Inspect Brake Power Booster Damaged booster vacuum line/check valve, or diaphram