Why is it......

rob-81 · Post by **rob-81** » Wed Sep 02, 2009 8:06 am

That sometimes my TGD sinks quickly and other times doesn't? Last week, I had five new spheres and new LHM. Since then, as well as a much improved ride, the back doesn't sink within minutes of stopping (new LHM? The old was very dirty). However, of the 8 or so mornings I have driven the car since the sphere change, on 6 ocassions it has seemed to be close to normal ride height after resting for 12 hours but on two ocassions, it has been nearly on the bumstops. Bit of a silly question I know but I'm just curious to know what causes this variation.
Thanks!
Rob

Post by **Tim Leech** » Wed Sep 02, 2009 9:07 am

I imagine the new accumulator sphere will have helped to keep the back end up as it will keep the system pressurised longer?

rob-81 · Post by **rob-81** » Wed Sep 02, 2009 9:14 am

I know the acc sphere keeps pressure up after switching off but I'm curious to know why sometimes it sinks quicker than other times.

DLM · Post by **DLM** » Wed Sep 02, 2009 1:09 pm

Things take a while to settle down after fitting new spheres, before setting into a pattern - which might well be different from the pre-change pattern. As it's been all-change on sphere and fluid front it may take a while to settle into that pattern.

I guess a dissertation could be written on the subject but the bottom line is really whether anything untoward is happening that you wouldn't expect from a 15-year-old-plus hydropneumatic Citroen. Doseur valves and rear struts leak back as they age but can generally be lived with.

(i) Is the car always parked in the same place and attitude and the same way round? Is it on a slope or not? Parking on a slope nose-end-up will accentuate any rear-end leakback, while of course the other way puts the weights and forces more on the front.

(ii) Push the rear down before getting into the car if it's still up after an overnight lay-up. If there is deterioration of the rear arm bearings they can provide a frictional resistance which keeps the rear end up in the absence of pressure before dropping suddenly. If this happens and there's metallic noise too they'll need attention.

Otherwise I'd just keep observing.

rob-81 · Post by **rob-81** » Wed Sep 02, 2009 3:10 pm

Thanks for that, I wasn't unduly worried, the sphere and fluid change seems to have given it a new lease of life, just curious really.

My old activa used to settle at some very strange angles at times - used to be very unsettling!!

Thanks,
rob

Vanny · Post by **Vanny** » Wed Sep 02, 2009 5:49 pm

that will be a knackered 'roll valve' on the Activa (or a knackered control unit).

Its perfectly normal to have different sinking times, if it was permanently up then you would be looking at a far greater problem ie lots of dirty and blocked valves and lots of replacement parts. Just be glad it doesn't have the Xantia break away rear height connector