I’m in the process of refurbishing the front brake callipers on a Discovery I, they are in a pretty poor state with two of the pistons almost impossible to get out. Looking at the LR manual and a couple of online videos it is stressed that the two halves of the calliper should not be separated. I have separated the two halves as it would have been impossible to service the pistons without in my view, particularly getting the pistons out and the seals back in.

I have put it back together with Loctite on the four bolts clamping the two halves together and all seems well.

Does anybody have any idea why these callipers should not be separated what the risks are by doing so??

When I did mine three years ago I had to separate the calliper halves to get the pistons out. I cleaned the parts, put in stainless steel pistons and new seals and they have been fine. No trouble at all. The only issue I know about is getting the correct O ring seals.

It might be because the relevant brake manufacturer & Land Rover didn't believe people could be trusted to torque the relevant bolts correctly on what is obviously a very safety critical part. Bolts were probably tightened to just below the bolts absolute limit in the factory & shouldn't be re-used