Is it just not releasing on the left front, or all the brakes? does it have ABS?
You need to check the flexible brake hoses at the calipers. Over time, moisture in the brake fluid lowers the boiling point of brake fluid. This can cause the interior walls of the rubber brake hoses to collapse. When this occurs, it allows the brake fluid to the calier when the brake pedal is pushed, but prevents the fluid from returning to the master cylinder, thus keeping the brakes engaged.
There is a simple test. Make sure you have a wrench that fits the caliper bleeder screw with you. Take a test drive and when the brakes start locking up, pull over. Open the bleeder screw and allow to bleed for a few seconds and then tighten. Now test drive to see if brakes have release(they will lock again in a few minutes). If they did release, then you just need to replace the hoses.
If they dont release, then you have a problem in the ABS hydraulic unit.