Help Bleeding Brakes

[Raptor44]

1941 Chevy Flatbed truck. Freshing this up, Motor rebuild some paint and body work. Installed new brake shoes, wheel cylinders, all lines. Installed a new duel master cylinder with vacuum boost and a proportioning valve. Have bled and bled the system numerous times and can not get a pedal. Tried doing it manually, and with a vacuum pump. No Joy. Anyone know the secret to getting this right. Any help would be appreciated. Thanks

 

[Duner Wi]

This might help if you did not bench bleed the master cyl. Usually there are instructions with new /rebuilt master cyl. as to bench bleeding.

https://www.youtube.com/watch?v=USdtwqju4GY

 

[John Saeli]

When we were doing outside shop work, after 3 days of being stumped one time, I discovered all 3 re-man cyl's I got and installed from the auto parts were bad. They didn't even supply the Vaseline.

 

[Raptor44]

Interesting. Could be. Put one of these Master Cylinder on the 47 GMC tow truck. Same problem.

 

[Raptor44]

Got both of these from Jegs. Said they would work. Got any vasoline left?

 

[John Saeli]

Are these re-man's? Just recently our son had a new M/C where a valve in there wouldn't let the brakes release. Pumped up fine, but held the brakes on. It is on a 1980 C60.

 

[Raptor44]

Well, tried another new and bigger m cylinder. Bled it on the bench installed bled and it still don't work. Thinking of just putting the single pot master back on and run it through the hydravac and see what happens.

 

[Longknife]

(quoted from post at 21:46:27 08/22/20) Well, tried another new and bigger m cylinder. Bled it on the bench installed bled and it still don't work. Thinking of just putting the single pot master back on and run it through the hydravac and see what happens.

Try letting it gravity bleed? Sometimes pumping the pedal makes bubbles that are hard to get out. are you getting anything at the bleeders??

 

[Raptor44]

Well after much fiddling. It would appear that the shaft for the master cylinder has to be perfectly plum for it to work. It can not be off one IOTA.