Xantia anti sink valve problem?

Gaskin · Post by **Gaskin** » 08 Jul 2006, 16:38

OK yet another Xantia suspension question, but I can't seem to find the answer in the previous posts. My Xantia estate begins to sink almost as soon as I turn the engine off. It does not drop further on restarting the engine (an indicator of flat rear acc sphere), but rises to normal height. All of the spheres are ~2yrs old, and the regulator clicks every minute or so. To me it suggests that the anti sink valve is not working. I'm not that bothered about this since it rises OK and brakes fine. But other than aesthetics does the antisink valve have any other function? Should I do anything about it? I'm fairly sure that the rear acc sphere is OK, but I did have to add ~200ml of LHM this morning.........

How long do spheres last? Mine have done 30,000 miles and I'd rather not change them all.

Cheers

Duncan

AndersDK · Post by **AndersDK** » 08 Jul 2006, 19:18

A bit more precise on the indications please :
1) does BOTH front & rear sinks as soon as engine is stopped ?
2) or is it rear only ?
3) or is front only ?

The sole purpose of the anti-sink (SC/MAC) system is pure cosmetic - to avoid the dreaded "tired camel" syndrome when starting your citroen in the morning. But most will find the function comfortable as well - not bending down in a low Citroen and crawl into it

Its by far impossible to give sensible life expectancy figures on spheres.
But the fact is that the nitrogen gas slowly diffuses out over time - indepedent of usage and high/low suspension. Then of course there is always the risc that the sphere membrane ruptures (rare).
As a rule of thumb you should have some 6years of usable service life from a sphere.

The hydraulic system does not consume hydraulic oil - but displaces it various places in the system. The main cause to minor topping up over time is brake pads & discs wear - as then the pistons must compensate and protrude more & more from the calipers. Hence more hydraulic fluid is needed to fill the caliper cavities.
But the evident gas diffusing will also cause topping up over time - to compensate for the lost gas volume.

FrenchLeave · Post by **FrenchLeave** » 08 Jul 2006, 20:59

It may be the anti-sink valve that's leaking, but it's unlikely. What is certain is that you have an internal leak from some item, maybe a rear suspension unit or the brake valve. All internal leakage fluid is returned to the hydraulic (LHM) tank so I suggest you disconnect the return lines one at a time at the tank to see which one is showing a noticeable flow of fluid. Then consult the hydraulic circuit diagaram to find out which component is served by that particular return line.

Derek

Gaskin · Post by **Gaskin** » 09 Jul 2006, 23:06

Both ends sink. It is not so rapid that you can see it sinking, but after 10 mins or so then when you start it up it rises at both ends. I haven't looked at the return pipes yet, what sort of flow rates are we talking about?

Cheers

Duncan

Mandrake · Post by **Mandrake** » 10 Jul 2006, 05:54

Gaskin wrote:Both ends sink. It is not so rapid that you can see it sinking, but after 10 mins or so then when you start it up it rises at both ends. I haven't looked at the return pipes yet, what sort of flow rates are we talking about?

Cheers

Duncan

Umm,

This might be an obvious point, but it's normal for it to lift when you get in and start it, unless you were sitting in the car the whole 10 minutes without getting out

When you get out of the car the height will spring up due to the weight reduction and as you walk away from the car the height correctors will make a downwards correction.

When you next get in the car it will now be too low, but it probably won't have enough stored pressure to lift until you start the engine, at which time it will lift a small amount to correct for the increase in weight - all perfectly normal behaviour.

Or have I missed something ?

Regards,
Simon