72 c50 brake problems

[68chevycst]

I have a 72 c50 and I can't seem to get a good brake petal, I have to pump the petal a few times to get a good petal. Once I have pumped it and push the petal to stop my passenger rear duals lock for a second. I have blead the brakes twice now and is doing the same thing. Do I need to adjust the brake shoes? I haven't pulled the drums yet to look. Any ideas?
Thanks,
Seumas

[rkn463]

Originally Posted by 68chevycst

I have a 72 c50 and I can't seem to get a good brake petal, I have to pump the petal a few times to get a good petal. Once I have pumped it and push the petal to stop my passenger rear duals lock for a second. I have blead the brakes twice now and is doing the same thing. Do I need to adjust the brake shoes? I haven't pulled the drums yet to look. Any ideas?
Thanks,
Seumas

On the corner that locks check for shoes contaminated with brake fluid or oil from the axle. I never understood how a lubricant can make them grab but it does. Regarding the need to pump them up make sure the adjusters have the shoes tight to the drums without dragging, if that is good then I'd flush all the fluid, bleed them and see if that gets it. If not then maybe a bad master cylinder.

-Richard