Hi you'll.. I have a 93 GMC Sierra stepside reg cab truck that i'm working on for the stepson.. It has been parked for a few years and the driver rear wheel cylinder leaked and froze up the brakes.. So replaced both rear wheel cylinders and rebuilt the 2 front calipers, and also had the rear drums and the front rotors turned... Removed all the old brake fluid and cleaned out the reservoir.. Added new brake fluid, and started the bleeding of the brakes... Here lies the problem i'm having.. Back brakes bleed just fine. started furthest away from the master cylinder working forward.. My front brakes will not bleed.. I'm not getting any fluid to com outta the bleeder screw, even took the line off and tried pumping the brakes and nothing.. This truck has an ABS system on the rear only and yes I held the combination valve in.. Tried it both ways.. Am I looking at rebuilding or replacing the master cylinder? The system was bleed with the pump, pump, pump slowly and hold while I turn the bleeder screw with a hose running into a glass of brake fluid.
