Front brakes locking up or not releasing can be a serious safety problem. There are many issues that could lead to front brakes grabbing, locking up or not releasing. These problems are more prevalent in areas of the country with harsh conditions such as snow and freezing temperatures. The reason is because of the corrosive salt and chemicals used to melt ice in the winter months. The first area to investigate would be the calipers and spindle attachments.
Unsnap the master cylinder lid, and check the fluid condition and fluid level. Put on a pair of latex gloves. Use a shot glass and dip it into the master cylinder. Hold the shot glass up to the light and inspect it for cleanliness. If the fluid is dirty replace it. Place the master cylinder lid on top of the master cylinder, but don't latch it until the troubleshooting is complete.
Loosen the front lug nuts, but do not remove them. Raise the front of the vehicle by placing a floor jack under the front center frame and jack it up. Insert jack stands under the frame as close to each wheel as possible
Spin the wheel and check for unobstructed rotation. Apply the brakes and check again for brake drag. If an obstruction is felt after applying the brakes, remove the lug nuts and wheels.
Proceed to the rear of the vehicle, have someone push the brake pedal and notice if the brake light comes on and goes off immediately. If the brake light does not go out immediately when the pedal is released, inspect the brake rod to be sure the brake pedal is retracting as it should.
Saddle a C-clamp over the caliper and push the piston flush into the caliper.
Remove the bolts that attach the caliper to the spindle. Remove the caliper from the spindle and remove the brake pads from the caliper. Take note of the brake pads so they can be reinstalled in the same position.
Insert a small, 2-by-4 block, into the removed caliper. Push the brake pedal to force the piston from the caliper against the block. With the piston protruding from the caliper, use light emery cloth sandpaper to clean corrosion from the exposed piston.
Spray a little penetrating oil onto the cleaned piston, use the C-clamp to push the piston back into the caliper. Place the brake pads back into the caliper in the same position as they were removed. Reinstall the caliper and pads onto the spindle.
Push the brake pedal while someone watches the caliper extend out against the brake pads. Note if the caliper piston retracts into the caliper after the pedal is released. The rotor should rotate without obstruction. If not, replace or rebuild the caliper. If the caliper checks out, proceed to the next step.
Remove the front brake line from the master cylinder. Insert a pressure gauge into the line opening. Push the brake pedal. If the master cylinder is working properly, the needle should go up and return to zero instantly when the pedal is released. Remove the gauge and reinstall the brake line into the master cylinder.
Replace the wheels and tighten the lug nuts. Remove the jack stands and lower the Caravan back onto the ground. Snap the lid back onto the master cylinder.
