XM Suspension problem

If I raise the suspension level in my XM and then set the control back to 'Normal' again, the suspension does not level out correctly. The back seems
to be OK but the front seems high. If I drive it in that state the front suspension is very bouncy.
I can sometimes fix it by lowering the suspension to the lowest setting and then raising it again to normal.
What is the most likely cause of this problem and is it fixable by a competent amateur?
Also, is there any detailed information online about how Citroen suspension works?
Thanks,
Rudge
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they were saying:

<chuckle> Your mate's already asked this over on the CCC member forums...

Almost certainly a sticky height corrector - how often's the fluid been changed in the past?
It's not difficult - but you MUST support the car properly before getting under it. Dropping a ton and a half of XM on your head by depressurising the suspension suddenly can rather spoil your whole day.

http://www.citroencarclub.org.uk/ds gives all the theory and practice behind the DS suspension - there's no real difference in concept to the XM, except for the Hydractive (go to the main bit of the site, and there's an article there on how that works, under the XM in "About the Cars"
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gurgled happily, sounding much like

Thanks for the info Adrian.
I will try replacing the LHM fluid. I believe I will require about 5 litres of the stuff. I can get a 5 litre can of LHM Plus for about 24. Does the Haynes manual describe the best method of draining the old LHM fluid out of the system? Or is there any 'tips of the trade' that I should be aware of?
Regards, Rudge
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they were saying:

What colour is it currently? It _should_ be a violent electric green. If it's not been done for ages (should be done every couple of years), it'll be filthy black. If it's bad, it's worth putting some flushing fluid in (available from GSF and others), leaving it in for a thousand miles or two, then changing for new LHM.

It's straightforward.
Start the car. Put it onto full flat. Turn it off. Remove the LHM tank - IIRC a couple of clips - and empty it. Give it a good rinse out (petrol's as good as anything) to get the old crap out. Clean the filters on the pipe block, too. Put the tank back in. Fill with new. Start the car. Full high. Up and down a few times. Check the level.
What are the spheres like? If the fluid's been that neglected, the chances are the spheres haven't been touched either. A flat accumulator - click-click-click-click from under the bonnet - will mean you have no reserve of brakes if the engine stops whilst you're moving. It also risks damaging other components by not damping the pressure waves from the pump. Flat front wheel spheres will not only mean you have no suspension, but will put extra stress on the rubber front strut tops, which can fail causing the suspension struts to come through the bonnet. There's 8 spheres on a late XM, less than £20 each. Most are easy to change, but there's a couple of buggers at the back - the anti-sink and rear hydractive centre. They are worth doing, though, as they make a big difference to the ride.
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<snip>

Can I high-jack this thread now to ask Adrian something about the CCC web site (IIRC you're the web master) - why does the site (appear to) use an absurdly short log-in cookie life. Why can't it use, in effect, an infinite time before dieing?
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much like they were saying:

Because it's a session cookie, unless you tick the box - at which point it remembers you for two weeks between visits.
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gurgled happily,

That's what I mean, why can't it die after say 5 weeks (or even until 'log-out') - two weeks is absurdly short time period for this class of site.
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much like they were saying:

The options within PostNuke (the CMS we're using) are "Not at all", "two weeks" or "forever".
Balance of opinion when the site was set up was "two weeks" being the best compromise.
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