'94 Disco Brakes - not balanced?

Just bought my Discovery I and knew it would be a bit of a project. I removed all 4 wheels and found the front brakes had been working hard, and the pads needed replacing and in fact, the rotors were damaged because some pads were down to the metal.

The rear brakes surprised me. The pads are not worn down. The rotors look rusty - Instead of shiny steel, they look like they've been in the lake for 17 years. Corrosion is built up over the whole disc, except one small ring where it is slightly worn away by the pressure of pads pressing against it. And this small ring is obviously where only 1/2 of the pad is actually making contact with the disc.

The calipers don't seem to be leaking, and there is no need to top up the brakes regularly.

Both right and left are the same.

New calipers?
Rotors okay, once I remove the 1/16th inch of rust ?
Is this an automatic brake control malfunction?

Have you tried opening the bleed screw and seeing if any brake fluis comes out?
If not, the brake valve RNI749 (Proline # PLI749) would be the most likely culprit.

When I bled the the brake lines, it looked milky. I think I will flush the lines, rebuild the calipers and try it then. Thanks.

Rebuilt calipers, freshly flushed lines and new rotors and pads. All good now.
I think the pistons in the rear calipers were seized.