Brakes Sticking

[LNielson]

I'm having some trouble with my hydroboost brakes on a '86 K30. The master sprung a leak so I replaced it. Now the brakes are sticking/dragging if I get on them hard, they release after a few seconds. I bled the master in the truck, and bled the lines thoroughly. The pedal feels good and the brakes work normally (no sticking) with moderate to light pedal pressure. Every time I hit them hard or push the pedal fully they stick/drag. This never happened with the old master.

The truck has been converted to 4 wheel discs with DIY4x brackets and I'm using stock 3/4 ton calipers in the rear with no parking brake, D60 discs in the front.

Has anyone experienced this before? What should I be checking? Could it be the proportioning valve/linkage setup on the rear axle of this 1-ton truck?

Thanks

 

[davo727]

Bad new master? Warrantee it and get another? ??

 

[resurrected_jimmy]

residual pressure valve from the old rear drum setup?

 

[LNielson]

Problem solved

I got my brakes going again! I took this opportunity to remove the rear weight adjusting proportioning valve and install an extended hose in preparation for a 4" lift. I thoroughly bled everything again including the master and now no more dragging. I have a new issue with the rears locking up before the fronts, but the pedal feels great and the brakes are working as good as before. I guess I'll be installing an adjustable proportioning valve to fix the rear bias.