89 S10 - The truck does not want to stop unless you pump the brakes. The master cylinder has been replaced and bleeding has been done on all four wheels. There is no loss in vacuum pressure so I can not figure out why it does not want to stop properly. Any help would be great.

Rear brakes may be out of adjustment. First, adjust the parking brake. The parking brake effects the ability of the self-adjusting mechanism to work correctly. Once the parking brake is adjusted, work the self-adjusting mechanism by backing up and firmly applying the brakes (just shy of locking the fronts). Do this 4 or 5 times and see what happens.

If this doesn't fix the problem I would try bleeding the system again. When you replaced the master cylinder, did you bench bleed it? Air can get trapped in the master cylinder and be very hard to remove through system bleeding. Your best bet might be to take it to a local shop and have the system pressure bled; all the old fluid and trapped air are purged and the system is completely charged with new fluid. If you truck has anti-lock brakes, then this will be your best bet at getting any trapped air removed.

mike

I've also seen sticking calpers cause the brake fluid to basicly boil which forced me to pump the brakes to stop