What year is this truck? Is it equipped with brake proportioning valves? Does it have ABS? Could you possibly PM me the VIN? I work for a GM dealer and I can get a lot of information about a C30 from the VIN.

/e Did you make absolutely sure you reconnected the same lines to the same ports?

Also, if you can successfully pump/bleed brake fluid from all 4 brakes, your problem might lie with something like the brake booster.

This post was edited by Santara on Oct 18 2017 04:55pm

Master cylinder?

Must be the flux capacitor

It may also be a problem with abs brake controller. If the motor is shot or something else is going on with the abs it will not allow you to bleed the brakes. You will have to bypass the abs system brake lines.