It's part of my standard routine after buying a hydraulic citroen. Usually it goes like this - engine oil & filter, fuel & air filter, replace spheres, drain lhm tank, wash out and clean filters, refill with hydroflush, drain 1 litre from each brake caliper and keep topping up lhm tank as you go. After somewhere around a thousand miles or so drain tank clean it and filters, depending on state of original lhm maybe refill again with hydroflush. On a part by part basis remove, strip, ultrasonically clean the regulator, height correctors, hydractive blocks. Usually I tweak the regulator whilst I'm at it. Eventually replace hydroflush with lhm after another tank and filter clean.
The amount of gunk that gets trapped in the valve work is surprising, even on cars with very clean lhm. I guess that's why in industry they back flush with hot fluid where possible. I'm still convinced that the sinkers stay supple with less maintenance than the anti sinkers. I also think there is very little movement of fluid after the the height correctors, sure it goes back and forth but how often does it get replaced with 'fresh' fluid unless you gave a excessive leak back problem and even then is it enough to flush gunk back to the filters in the tank?
This HC cme out of the XM SED that I have, the LHM in the tank was bright green -
All just my opinion you understand.
Thanks!