Brake intermittent lockup on 2000 Chrysler Town & Country

Recent master cylinder and front brake replacement. Since then after about 20 miles in stop/go and highway traffic. Brake pedal appears locked/firm and right front brakes locked tight. Pulling over and turning car off/on fixes the problem. All right front parts replaced. Still happens. Scary when it happens at 55 mph on highway. Repair shop unable to duplicate. Any ideas?

Asked by for the 2000 Chrysler Town & Country
Since this is confined to one axle, I advise you to Bleed the entire brake system. From your description, if sounds like air is in the system and as the brake fluid heats up, the air expands causing the caliper to drag. The more drag, the more heat, etc. Parking for a few minutes will allow the fluid to trapped air to enough to release the caliper. Also make sure that there is no contamination of the brake fluid as this will cause the rubber components to swell ane cause a number of braking issues. This is not an ABS related issue. One last note. If the master cylinder pushrod is out of adjustment, it can prevent the front brake calipers from releasing by blocking the fluid return port in the master cylinder. Check for oil, water, etc., on the pad or lining contact surface of all brakes. Lastly, the caliper may be defective.
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This sounds like a pretty major safety issue. The shop should be taking this seriously. Does this happen all day long? Does it only happen in the morning on your first drive? If it only happens after driving a certain amount of miles, they need to be test driving it at least that far. If you can duplicate it regularly, perhaps you can ride along with the shop foreman and tell them the conditions under which the caliper locks up.

Why did they replace the master cylinder in the first place?