I just finished rebuilding mine, it wasn't a big deal. In fact, the worst part was getting the stupid bolts out of the back of the caliper - you can't get any real large wrench arm in there without cutting your ability to turn it more than 2 degrees at a time. It literally took me about 2 hours of actual work just getting the 4 bolts out of the two calipers.
Don't take the caliper apart, follow the directions exactly in the Haynes manual. You really can get the pistons out using air pressure (about 15 psi).
Make it easy on yourself and unhook the caliper from the brake line and take just the caliper off -
don't mess with the bolts on the top of the steering ball unless you absolutely have to. Just deal with the leaking fluid - block it with a rubber cap - it is much easier than taking the mounting plate off the top of the steering ball!!!!!!
I went to a local LR shop (not a dealer) and bought just two pistons. I knew at least one would be bad enough to replace. You cannot buy single pistons anymore from RN, Atlantic Brit., or the dealer; they only come in packs of 4. When I got the pistons out I used a new set of seals - a bear to get into the piston housing, but possible - and I dicarded the two pistons that were in the worst shape. The two that were OK I cleaned with brake cleaner, and polished with a dremel tool with a felt pad and chrome polish. They turned out pretty good, at least when I got it all back together, bled the brake lines - use a partner to press the brake pedal while you work at the bleed screw - they brake the truck just fine, no pulling to the side, no warped disc feel and the pistons are all compressing at very closely comparable rates.
It is an easy job, but difficult to get done - like all Rover jobs, you have to develop techniques. Just buy 2-3 cans of brake parts cleaner and keep everything very clean. Go through the extra time to make sure the hub, caliper, and all other parts are free of surface rust, dust, etc, it will be worth it.
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