Sounds like one of the front brakes is locking up. You can prove this is the cause by putting the car in neutral, then trying to coast down an incline, or by pushing the car by hand. Also, on a flat surface, the car should move ahead on its own when idling in gear.
A number of things can cause a locking brake. Dirt and corrosion buildup on the polished sealing surface of a caliper piston prevents the piston from releasing. Years ago we cleaned or replaced the piston, but today it's just as inexpensive to replace the entire caliper.
Brake fluid contaminated with petroleum products will make rubber parts soft and mushy. They will grow causing return ports in the reservoir to become blocked. The trapped fluid will keep the brakes applied. Then, as the brakes heat up, the trapped brake fluid heats up and expands, causing the brakes to apply harder. If the fluid is contaminated, the rubber seals under the reservoir cap will balloon up and you won't be able to stuff them back in. Opening a bleeder screw will release the trapped fluid and the brake.
Another possibility that seems to becoming more common is a rubber front brake hose that's pinched off by rust buildup inside the crimp of the metal bracket holding the center of the hose. The brake will also release under this condition if the bleeder screw is opened. The fix is to open the crimp a little with a channel lock pliers. Replacing the hose, of course, will also solve the problem.
You are likely to find the car will move easily hours later after the trapped brake fluid has had a chance to work its way back up to the reservoir. The brake will lock up again after it's applied the next time.
Caradiodoc
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Friday, April 10th, 2009 AT 9:41 PM
