Brakes locking up.

There is a port timing hole in the fluid reservoir. The primary seal on the front of the piston in the master cylinder must return past this port when the pedal is released. This will release any pressure in the system due to fluid expansion when the fluid gets hot. It is usually a very small hole about .022 in. in diameter. Look to see that its there, it's not plugged, and you can push fluid past it by pushing on a brake caliper piston.