The first thing to do, when they lock up again, is to open the hydraulic system at various places to see where the pressurized brake fluid is being trapped. The easiest is usually to start right at the master cylinder. Loosen the soft metal line nuts about a half turn. If brake fluid spurts out, and the car is easy to push or wants to coast down a slight incline, we have to discuss the possibility of brake fluid contaminated with a petroleum product. If we're lucky, the brake light switch will be out-of-adjustment and holding the brake pedal down a little.
If that worked, get them to lock up again, then loosen the nuts holding the master cylinder to the power booster, and let it come forward about 1/8" to 1/4". If the brakes release, it has to be due to the brake light switch. If they still stay locked, remove the cap from the reservoir and observe the rubber bladder seal under it. If it is blown up and mushy, the fluid is contaminated. The repair for that involves replacing every component with a rubber part that contacts the brake fluid, including the new calipers, flushing and drying the steel lines, then installing all new components, filling, and bleeding the system. That gets to be a very expensive repair.
If the brakes do not release when you loosen the lines at the master cylinder, open the bleeder screws on the front calipers. If one of those lets the brakes release, the best suspect is the rubber flex hose for that wheel. There's a mounting bracket crimped around the middle of the hose. Rust builds up inside that crimp and constricts the hose. It's easy to force brake fluid through that restriction, but the fluid won't flow back to the reservoir when you release the brake pedal.
Let me know what you find up to this point.
SPONSORED LINKS
Saturday, May 22nd, 2021 AT 5:36 PM
