Sinking xantia rear suspension

pete@co.uk · Post by **pete@co.uk** » 30 Jan 2005, 19:16

Hi guys
Im planning to replace the rear suspension spheres on my 94 xantia 19 diesel sx because the ride is hard on the rear. My question is after ive replaced them will that stop the back end from droping to its lowest setting overnight becouse everytime i start up in the morning i have to wait till the suspension comes up to its right height before i can drive off is that normal for this age of car or is it the spheres.
any ideas
pete..........................................

nick · Post by **nick** » 30 Jan 2005, 19:23

Does your car have anti-sink ? (With a sixth sphere at the back)
If not, its normal for the rear to sink completely overnight.

modi · Post by **modi** » 30 Jan 2005, 20:22

I replaced the rear suspensions 3-4 weeks ago and since then the rear doesn't sink over night as it was before, but it sink then raise when starting up the car, I have a sphere in the middle in the back and I think its anti-sink and I am not sure if it has anything to do with whats happening.

nick · Post by **nick** » 30 Jan 2005, 20:28

Staying up overnight, but sinking then rising back up again when the engine is started is usually a sign that the anti-sink sphere needs replacing.

pete@co.uk · Post by **pete@co.uk** » 30 Jan 2005, 22:10

hi guys
Thanks for the info ill have to have a look for the anti sink sphere is it situated between the other two?

nick · Post by **nick** » 30 Jan 2005, 22:15

Slightly forward of the other two.
As a general rule if your car has the Citroen badge on the bonnet and a two spoke wheel with no airbag it won't have anti-sink.
If it has the badge on the grille and has a four spoke wheel with drivers airbag it will have anti-sink.
The changeover point was mid 1994.

modi · Post by **modi** » 30 Jan 2005, 22:24

My car has Citroen badge on the bonnet with no airbag but there is a sphere in the middle in the back between the tyres, is it anti-sink sphere??

nick · Post by **nick** » 30 Jan 2005, 22:46

Yes, and if you unscrew it don't make the mistake I once did of not removing the pipe connection from it first !

nick · Post by **nick** » 30 Jan 2005, 22:49

...sounds as though Citroen overlapped a few features from both the old and the new models on some Xantias - typical !

pete@co.uk · Post by **pete@co.uk** » 31 Jan 2005, 02:49

Hi guys
Thanks for the advice nick ill have a look tommorrow underneath my car and see if there is a anti sink sphere my xantia has got the badge in the centre of the bonnet and no airbag so the chances are i have no antisink sphere according to what you say. So my guess is i,ll still have the rear sinking down even after ive had the spheres replaced. Anyway ive got to get those spheres done because the ride in the car is so hard it jolts my back everytime i go over a bump, anyway ill let you all know how i get on
Thanks again
pete.................................

FrenchLeave · Post by **FrenchLeave** » 31 Jan 2005, 04:42

Hi,
Are you sure the sphere in the centre is the anti sink sphere? If it's dirctly screwed into a valve block which has a number of pipes (four I think) connected to it then it's the hydractive valve and sphere.
The so called anti sink sphere is a misnomer. Its sole purpose in life is to provide fluid under pressure to the rear brakes in the event of main hydraulic failure when the anti sink valve would close, shutting off the rear suspension from the brakes. The rear brakes normally get their supply from the rear suspension of course.
Best wishes in your search for a cure - if you're not careful you'll end up changing everything and paying a fortune for the privilege.
FrenchLeave

pete@co.uk · Post by **pete@co.uk** » 31 Jan 2005, 22:13

Hi guys
Thanks for reply French ive actully this afternoon had my rear spheres changed on my xantia and there is no centre sphere there, and i think French might be right about the anti sink sphere. i asked my local independent citroen specilist who fitted my new spheres today and he said somtimes they do tend to sink and some don,t he said all xantias very in what they do and they all seem to have a mind of there own. Anyway i now have the "magic carpet ride" back, much better than hitting your head on the roof lining everytime you go over a bump [:D]. It remains to be seen now if it sinks down now tomorrow morning ill keep you all informed of what happens.
pete...........................

Kowalski · Post by **Kowalski** » 31 Jan 2005, 22:44

When my '95 Xantia was sinking when the engine was started it wasn't the anti-sink sphere, it was the accumulator sphere that needed changing.
I'm not exactly sure why the car sinks when the accumulator is flat, my thinking goes as follows. When the engine starts, the hydraulic pump pressurises the hydraulic system normally this takes alittle time because the accumulator sphere needs to be pressurised, but when an accumulator is flat, it can't store very much pressure, so the hydraulic system pressurises very quickly. Once the system is pressurised enough, the anti-sink valves open, the rear height corrector is open (because even cars with anti-sink do sink albeit very slowly) there is no pressure available to raise the rear suspension, in fact the rear suspension has a higher pressure than the high pressure part of the hydraulic circuit, so the hydraulic fluid flows out of the rear suspension and the rear of the car falls.
When a good accumulator sphere can hold pressure, it can use this pressure to pressurise various bits of the hydraulic system that need to be pressurised, e.g. anti-sink sphere, brake valve etc, so the car doesn't use its rear suspension pressure to pressurise the systems.

pete@co.uk · Post by **pete@co.uk** » 02 Feb 2005, 17:40

Hi guys
Update
Well the sinking on my xantia 1.9d sx is still there a bit but not so bad as it was since i had the rear spheres replaced the other day in fact now ive had the rears done it seems to be showing the front spheres up when i go over the speed bumps round here at a slow speed the front seems to be hard but when the rear wheels go over you hardly feel a thing so i think the fronts are due for a change now. As for the sinking well looks like im going to have to live with it.
thanks for all your help guys
Pete..............................................................

Kowalski · Post by **Kowalski** » 02 Feb 2005, 18:19

You could live with the sinking or you could change your accumulator sphere, whichever you're happier with...