Weak Brake Pedal
 

I am having trouble with the brakes on my brother's 1969 GMC C15. The truck stops but the brake pedal soft and under hard braking the wheels don't lock up. I have replaced the master cylinder and the rear left wheel cylinder (busted bleeder valve). I also swapped out the portioning valve with an old one I had lying around. The rear shoes and drums looked good. I believe the rear brakes are not getting the correct amount of pressure. When I bled the brakes the front cylinders shot out a stream of fluid but the rear cylinders only dribbled out. Is there something that could be causing this?

Re: Weak Brake Pedal
 

that truck should not have a proportioning valve// it had a distribution block from the factory which is completely different

Re: Weak Brake Pedal
 

That explains a lot. I was wondering why a drum/drum truck would need a portioning valve.
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