Left front brake caliper locked up, what causes

Check your brake line for twist or collapsed internal portion.

The hose could be collapsed internally holding residual pressure and keping the pads applied. Also make sure that the caliper is sliding free side to side.

it could be a flex hose between the caliper and the steel line

I would take it up with the guy who put the caliper in. if that was you i would get it up in the air and see what you did to cause this. take a close look at the parking brake mechanism and cable, used to see frozen cables cause this on drum brakes

Dear Smoking And Locking.......
It sure sounds to me like you are having a brake issue on the lf of your vehicle..Obviously your lf brake assembly is not releasing.You could have a seized caliper, a restricted lf brake hose, a restricted brake line, or pad material that is unsafe, it's time to get those brakes inspected ASAP!!!! Brake repairs on that year of vehicle are fairly simple for the first timer....if you need any more help just get back to me ...THX HOPE I COULD HELP!!

You have a new defective master cylinder, happens all the time. pull it off and take it in for an exchange and buy new not rebuilt. The rebuilts do not last.

Most possible reason is a seized piston in the right hand caliper, did you just replace the one side or both?

could be the calipers/also hoses on calipers. ur brake fluid coul be contaminated by now,if u take the master cylinder top off and the gasket (on the lid) is swelled up,then u know taht it is. replace the mastercylinder and wheel cylinders,and calipers and all hoses,this is the only way to prevent brakes from failing,,along with bleeding all the old fluid out,sounds a little expensive ,but the only safe approch

Sounds like the caliper needs replaced. Sometimes the pistons lock in the caliper and cause the brakes to drag. When the mechanic changed the brakes before, he pushed the pistons in all the way to accomodate the new brake pads. Now that they are wearing back down, it is getting to the warped spot in the caliper and starting to stick.

Dry-fit them. Bleeder screw is always on the top of the caliper if installed on the corret side.