I am having problems bleeding the brakes on my 66 Chev 1/2ton. I just recently upgraded fromt he stock single line master cylinder to a dual cylinder from a 68 Chev 1/2ton. The lines are plumbed with 1/4" line as per stock. With one line going to the front and one to the back. No proportioning valve.

I bench bleed the master cylinder and had no problems there. But when I tried to bleed the brakes last night I am getting next to nothing at the wheel. I could pump the pedal a million times , and probably did, still nothing happens. I left the wheel cylinder open last night to gravity bleed the system, but did not work. Maybe 1 ml of fluid in the catch can this morning.

Any ideas? I am going to re bleed the master cylinder right now and try again.

Thanks
Steve

I'd say your rubber brake line at the wheel is colapsed.

They will act like a one way valve and either make the caliper stick, or become completely blocked.

All 4 wheels? :D I tried them all and nothing. There is actaully a little tiny bit of flow. After 50 pumps it will push fluid about 3 inches down the drain tube. When you stop pumping it gets sucked back up. So there is flow persay.

Thanks
Steve

You need a combination block for sure. I think you have stuck the piston all the way forward in the master cylinder. Easy to do when new. You have to be sure not to depress the brake rod all the way when you bench bleed.

[http://www.mpbrakes.com (http://[http://www.mpbrakes.com) for more tech info.


Also, when you change the master, you should bench bleed the master, then, bleed from the master's lines into the combo block, then to the wheels. Do not leave the system open, that draws moisture, and could cause rust.

Thanks, I'll check it out. Starter went on my Cutlass so it will be a while before I can get to it. Anybody know if a factory 68 1/2ton had a proportioning valve? Obviously my 66 never did with a single line.

Without a pro. valve is there any problems with bleeding half the master cylinder while the front is still closed? As in when I am bleeding the front, should it be allowed to flow fluid, or closed? Since the front and back are completley seperate.

Steve

I use the hand vacume pump to bleed works great. I also installed check valve bleeders.

I am definetley considering a vacum pump. But then again I have been considering it for the last 3 brake jobs. :D

Thanks Guys
Steve