1997 GMC Sierra Brake Question?

[Alex E]

Replaced calipers, replaced brake lines, rebuilt master cyll but when brakes are applied the front calipers do not immedeately release. After it sits for five minutes or so the calipers will then release allowing rotors to turn. When you open the bleeder valve the calipers will then release with minimal effort. Original problem was front brakes over heating due to slight application of the pads to calipers with pedal released driving down the road. I thought one of the above would cure it but no go so far. Any ideas? I am at my witts end with this darned thing.
Unsure of the block you speak of but will check. The ABS pump seems to not be clogged as I have not loosened the lines to it yet.

Yes I did change the rubber brake lines to both the front calipers.
Yes I put on a rebuilt master Cyll.

 

[kelly_f_1999]

check your brake fluid control block
look at where brake lines meet or come together is a small block that control flow of fluids

 

[hurchelfox]

you've never suspected the master cylinder?..... i've found that collapsed brake hoses were the culprit most of the time. i hope you just didn't start slapping on parts. i wish you luck. make sure you've bled the system real good. doug