Vehicles that sit in one spot for extended periods can develop surface rust on brake components. If enough rust forms, the brakes can seize up. One of the first steps toward putting the vehicle back on the road would be to loosen the brake system. Some brake components may have to be replaced.
Attempt to move the vehicle. In many cases, simply moving the vehicle in reverse for a short distance can cause the calipers or shoes to break free from their rust bonds. If moving the vehicle does not work, proceed to the next step.
Remove the wheel and tap the calipers with a rubber mallet. The vibration may loosen up rust to free the calipers. If you have drum brakes and the brake shoes are stuck on the wear ridge within the drums, rotate the drum until the access hole lines up with the adjuster inside. Use a flathead screwdriver to turn the adjuster counterclockwise until the adjuster hits a stop. In many cases, the shoes will retract from the drum surface.
Check the parking cable to determine whether it's frozen. If the parking brake was applied, disengage it to reduce tension on the cable. Follow the cable to the rear axle and pull the cable hard to one side. If the cable is not seized, it should be loose at the drum end.
If the brake drum will not rotate, use a brake drum puller to break the drum free. Attach the brake drum remover to the drum and use the manual screw to pull the drum outward while tapping on the drum with a rubber mallet in a radial motion. The drum should break loose from the brake assembly. Inspect the assembly for rust and replace components as necessary.
Remove the caliper from the brake disc and place a block of wood in between the pistons. Gradually press the brake pedal until the pistons are pushed out of the caliper. The block of wood will keep the pistons from popping out with excess force. Use a wire brush and brake cleaner to clean off the surface rust or replace the caliper, if necessary.
Do not use WD-40 or other penetrative lubricant directly on the brake hardware. This can leave a slippery film that can reduce the effectiveness of the brakes.