When we bought the truck one of the first jobs we did was to check the brake calipers. Although most motor manufacturers advise you to change the brake fluid every year, few owners or garages seem to stick to this recommendation. And especially in the UK water seems to find a way into the brake line. Low and behold that happened on our truck as well. One of the rear calipers had water leak past the rubber seals and it started to corrode. So much so that we could not remove one of the pistons. We sent the rear calipers off to be reconditioned, and ordered new seal kits (Toyota) for the front calipers. Fitting these were fairly straight forward. Before we refitted the calipers to the car we did a complete flush of the brake line to get all the old contaminated fluid out. We pushed about two bottles worth of fluid throught the system. Brakes working fine now.
We painted them as well