Xantia 1.9 TD Suspension

soupy_sam · Post by **soupy_sam** » 23 Aug 2006, 17:26

I have replaced the 2 front spheres over wheels. all was fine until I took our caravan 2000 miles round France car towed and drove great. Now the rear of the car drops when I park and although it comes up to height when engine started the ride is very HARD and bumpy.

Can you tell me what needs doing to the old girl now please

Post by **Peter.N.** » 23 Aug 2006, 17:39

Very hard and bumpy just at the back? Could be those spheres need replacing as well, and the centre one if its hydractive. Theres nothing else except a mechanical failure that will cause a hard ride. Try 'bouncing' each corner of the car with the engine running, you should have about 4" - 6" of movement, stiffer at the front, if you havn't, replace the appropriate spheres.

soupy_sam · Post by **soupy_sam** » 23 Aug 2006, 18:49

how do I know if it is Hyrdractive?

steelcityuk · Post by **steelcityuk** » 23 Aug 2006, 20:22

Only VSX & Exclusive models have Hydractive. Also Hydractive cars have a switch that allows the driver to change the setting. On Mk 1 Xantias it's near the height control whereas on MkII Xantias it's on the dash near the steering wheel.

Steve.

Post by **Peter.N.** » 23 Aug 2006, 22:08

KP · Post by KP » 23 Aug 2006, 23:04

As well its worth noting that there is a rear accumulator sphere. id say for the hassle its worth doing this at the same time as it saves another trip under the car, especially with the weather only getting worse

May not be needed just yet but think of it as knowing when they have all been done and if the rear spheres have gone the accumulator may have been working a bit harder sometimes..

mezuk04 · Post by **mezuk04** » 24 Aug 2006, 07:53

Are we allowed to call the rear sphere an accumulator sphere????

I believe it was just an Anti-Sink sphere, and not an Accumulator sphere?

Or is the principal merely the same? and the name different!

citronut · Post by **citronut** » 24 Aug 2006, 08:49

when you ask GSF for rear spheres on a car with centre spheres they usualy recomend you fit a new centre at the same time
regards malcolm

Post by **Peter.N.** » 24 Aug 2006, 10:46

Mezuk - I think rear centre spheres and anti sink are different things, never having had 'anti sink' I am not familier with them, but the center rear sphere is very similar to an accumulator sphere in that it has no restriction in it, that's why the suspension is soft in the 'electro valve' open mode, and thats also why if you only change the outer ones and the centre one is flat it makes very little difference to the ride.

Mandrake · Post by **Mandrake** » 24 Aug 2006, 11:11

Just to clarify a couple of points here -

The Hydractive centre spheres do indeed have no damping valves in the spheres themselves, they're built like accumulator spheres - in fact the rear hydractive centre sphere is EXACTLY like the main accumulator but gassed to 50 bars instead of 62. (Fitting an accumulator sphere which has dropped to 50 bars is a common trick apparently, at least in countries where new spheres are expensive)

However there are TWO damping valves mounted in the control block the sphere is screwed to - one going to each side, and they are exactly the same construction as the damping valves normally found in spheres, so its not fair to say that there is no damping for the centre sphere - its just in an external location.

(And it's also true to say these centrally located damper valves are tuned a lot softer than the outer strut sphere damper valves both in terms of the bypass hole diameter and the opening threshold of the washer valves)

As for the anti-sink sphere - it too is like an accumulator sphere with no damper valve in it, but it also has a pipe union fitting in the end. Another name for the anti-sink sphere would be "rear brake accumulator".

The anti-sink system works by isolating the leaky system elements from the suspension when the main system pressure drops below the suspension pressure when the car has stood for a while - in the case of the rear suspension the leaky elements are the height corrector and brake doseur valve.

Unfortunately isolating the doseur valve means the rear suspension pressure can no longer act as a source of emergency braking if the main system pressure that runs the front brakes dissapears - so the anti-sink sphere acts like an accumulator that supplies pressure to operate the rear brakes after the anti-sink valve has closed.

If the anti-sink sphere is completely flat (punctured diaphram for example) there would be little outward sign that anything was wrong, (perhaps the rear going down a bit sooner) but in the unlikely event of the main system pressure failing completely, the rear brakes would ALSO fail at the same time as the front brakes.

For that reason alone it's a good idea not to forget the anti-sink sphere just because it "doesn't seem to do anything"....

Because the anti-sink sphere is mounted centrally at the rear, while the "hydractive centre sphere" is actually mounted relatively far to the right, refering to the "rear centre sphere" is a bit ambiguous, and people often mix up the two...

Regards,
Simon

mezuk04 · Post by **mezuk04** » 24 Aug 2006, 11:15

Hmm, I thought we would be assuming it to be a standard Xantia until it was confirmed to be different!

My reference was referring to the mention of the Accumulator sphere (at the radiator) and the anti-sink rather than the involvement of any 'extra' spheres

Post by **Peter.N.** » 24 Aug 2006, 12:35

I stand corrected

My XMs have all only had one extra sphere in addition to the outer ones so by default I called it the 'centre sphere'.

mezuk04 · Post by **mezuk04** » 24 Aug 2006, 13:03

Peter.N. wrote:I stand corrected My XMs have all only had one extra sphere in addition to the outer ones so by default I called it the 'centre sphere'.

Im confused.

So when you refer to your XM's 'centre sphere' are you referring to the anti-sink sphere or the radiators accumulator sphere......OR something 'extra'

soupy_sam · Post by **soupy_sam** » 24 Aug 2006, 13:59

How do you UNDO the rear spheres I have tried everything I can think of and they wont bugde???

mezuk04 · Post by **mezuk04** » 24 Aug 2006, 14:17

Theres a couple of ways really, the one i can think of is.

Put the car on highest setting, this makes everything rock solid, then try and budge the spheres a little (with a chisel and hammer or some brute force or even with a big pair of clamps) once you have managed to turn it a little.

Then go through the correct procedure for removal....car on low, depressurised and spheres removed.