i have a 1987 s1900 international with hydroboost. it has disc all the way around. i replaced the master cylinder when i bought the truck. i replaced the font brake pads and had both rotors turned and rebuilt both front calipers. the pass. front got hot and seemed to be sticking. i replaced both hoses on both sides from the steel lines to the calipers. that did not fix it. i then replaced the caliper. it did fine for 2 trips then it got hot again. i then blew out both front lines from master cylinder to the calipers. nothing. i took two short brakes lines and put them above the master cylinder and started the truck and ran it for 10 minutes or so and no fluid came out. i can see when you press then depress the brake pedal the caliper clamps down then releases but i then jack the truck up and it has drag on it. i did check the oil in the hub and its full and cool to the truck so i know it is the brakes. could my hyroboost be weak or what? why is just this one side not releasing fully? there is electric motor below the master cylinder. what is this for? thanks in advance shannon
That braking system is actually power assisted brakes, the system uses power steering hydraulic pressure to assist the brakes. The electric motor runs when the key is on, but engine is off to provide back-up braking assist. There is a flow switch that will sense when the engine is running and turn off the electric motor. It sounds like either the caliper is not sliding side to side freely and getting jammed up, or the sliders/mounts are that worn and the caliper is now sitting crooked and getting jammed.
