F350 1972 rear brake problems dual wheels

[hippychick_67]

Put new brake pads,new master cylindar. but still back brakes not working. Any advice would be appreciated.

Thank you

[unclebubbles]

Originally Posted by hippychick_67

Put new brake pads,new master cylindar. but still back brakes not working. Any advice would be appreciated.

Thank you

You didnt give us a whole lot to go on, but here goes. First, make sure you bled the system and got all the air out. Bleed front and rear, till you get fresh, clean fluiid, and no air. Are the rear brakes not functioning at all, do you have some rear brakes, are the shoes moving at all when you mash the pedal? Are you having to add fluid to the master cyl. , could be a pinhole rusted in a line to the rear? Several things can cause this. The rubber line at the rear, could be deteriorated inside, and collapsing, blocking the flow. This happens often in older vehicles, front and rear. Check for good flow at the bleeder screw. Another likely culprit, is the proportioning valve. It controls the distribution of fluid, front to rear. It will be frame mounted on the drivers side, usually, just follow the lines from the master cyl.. If youre not getting good fluid flow to the rear, and the rubber hose is good, this is likely the problem. I have got rebuilt master cyls. before that were defective, but this is unlikely. Good luck
Later
Ed
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