Hi,
I don't know the purpose of the central rear accumulator in the Xantia model 1997 (Not Hydractive System). Can you help me?
TKS Massimiliano.
Xantia accumulator
Moderator: RichardW
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DarkendViper
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My car does this. It's a 1996 Xantia VSX Estate with Hydractive II (I think). Sometimes when you turn it off the back end drops fairly soon. Other times it stays where it is. When it stays up the next time it's started the back end sinks after the STOP light goes out.
Where about's is this sphere located?
Ste
Where about's is this sphere located?
Ste
Maxx,
The STOP light referred to is a warning light on the dash board indicating that the car has a problem. You may well see it when you first start the car until the hydraulic system is fully pressurised. When it goes out, all should be well.
It may also come on if another of the warning systems is triggered say the water temperature is over heating.
Phil
The STOP light referred to is a warning light on the dash board indicating that the car has a problem. You may well see it when you first start the car until the hydraulic system is fully pressurised. When it goes out, all should be well.
It may also come on if another of the warning systems is triggered say the water temperature is over heating.
Phil
Hi Massimiliano -
There's no direct relation between the accumulator and the STOP light.
As others mentioned - the STOP light should be considered a "master caution" lamp in a Citroen - notifying the driver that something serious is at fault.
The STOP light is then lit - together with the warning light for the failing subsystem.
Other than engine sensors - there are 2 sensors in the hydraulic system that can lit the the STOP light (and the hydraulics warning lamp) :
1) the reservoir level float switch (low fluid level)
2) the safety valve system pressure switch (low system pressure)
A failing rear antisink (or rear brakes accumulator) sphere will then not be warned directly - but MAY be warned indirectly by causing a short term system pressure drop when pressure charges up - opens the safety valve - and charges the suspension.
The point is - that a failing rear antisink sphere NEVER FOR SURE will be warned by the STOP light.
Your original question is covered by RichardW.
I'll just add to this - that the antisink system is not just made up by the added rear center sphere - there is a special antisink valve incorporated separately into both the front & rear suspension.
If you want in-depth knowledge - read this document :
http://www.tramontana.co.hu/citroen/guide.html
There's no direct relation between the accumulator and the STOP light.
As others mentioned - the STOP light should be considered a "master caution" lamp in a Citroen - notifying the driver that something serious is at fault.
The STOP light is then lit - together with the warning light for the failing subsystem.
Other than engine sensors - there are 2 sensors in the hydraulic system that can lit the the STOP light (and the hydraulics warning lamp) :
1) the reservoir level float switch (low fluid level)
2) the safety valve system pressure switch (low system pressure)
A failing rear antisink (or rear brakes accumulator) sphere will then not be warned directly - but MAY be warned indirectly by causing a short term system pressure drop when pressure charges up - opens the safety valve - and charges the suspension.
The point is - that a failing rear antisink sphere NEVER FOR SURE will be warned by the STOP light.
Your original question is covered by RichardW.
I'll just add to this - that the antisink system is not just made up by the added rear center sphere - there is a special antisink valve incorporated separately into both the front & rear suspension.
If you want in-depth knowledge - read this document :
http://www.tramontana.co.hu/citroen/guide.html
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philhoward
If the STOP lamps distinguish very fast - it's likely an indication of a flat accumulator sphere - as the sphere then has no gas left to compress - and the pressure then builds up very fast.
I'd say a longer time on STOP lamp after the car has been left for longish - allowed to go completely flat - is a healthy indication.
As then all spheres has a a lot of gas that needs be compressed before the system is fully charged.
I'd say a longer time on STOP lamp after the car has been left for longish - allowed to go completely flat - is a healthy indication.
As then all spheres has a a lot of gas that needs be compressed before the system is fully charged.
Au contraire.
When you start the engine, pump starts filling the accu sphere with LHM, compressing the gas inside. Lower the pressure in sphere, more LHM is needed to compress the gas to 80-100 bar, when STOP goes off. Only if accu sphere is totally flat and there's nothing to compress, STOP will go off immediately.
I did the following test a few days ago. Switched the engine off and released a PR screw on the regulator for half a minute, to decompress the accu sphere. Then moved height lever to lowest and started the engine. It took 13.5 sec at 900 rpm for STOP to distinguish (at the same time car started to sink, because A/S valves opened). Assuming that this happened at 90 bar and that pump capacity is 0.9 ccm per engine revolution (for petrol models with 6+2 pump), I got following:
V = 13.5 * 0.9 * 900 / 60 = 182 ccm of LHM was filled into sphere
p = ((400 - 182) / 400) ^ 1.3 * 90 = 40.9 bar ... pressure in the sphere at rest
Next week I'll probably visit my mechanic, because front spheres needs some fresh gas, and we'll also check how close I was with this.
When you start the engine, pump starts filling the accu sphere with LHM, compressing the gas inside. Lower the pressure in sphere, more LHM is needed to compress the gas to 80-100 bar, when STOP goes off. Only if accu sphere is totally flat and there's nothing to compress, STOP will go off immediately.
I did the following test a few days ago. Switched the engine off and released a PR screw on the regulator for half a minute, to decompress the accu sphere. Then moved height lever to lowest and started the engine. It took 13.5 sec at 900 rpm for STOP to distinguish (at the same time car started to sink, because A/S valves opened). Assuming that this happened at 90 bar and that pump capacity is 0.9 ccm per engine revolution (for petrol models with 6+2 pump), I got following:
V = 13.5 * 0.9 * 900 / 60 = 182 ccm of LHM was filled into sphere
p = ((400 - 182) / 400) ^ 1.3 * 90 = 40.9 bar ... pressure in the sphere at rest
Next week I'll probably visit my mechanic, because front spheres needs some fresh gas, and we'll also check how close I was with this.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Lower the pressure in sphere, more LHM is needed to compress the gas to 80-100 bar, when STOP goes off. Only if accu sphere is totally flat and there's nothing to compress, STOP will go off immediately.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Au contraire ? - mais non mon amis :
- right - because any sensible residual pressure will still empty out the acc. sphere while car is resting - making for time to recharge the sphere's LHM cavity. If no pressure left at all (completely flat) - the LHM cavity in the sphere won't empty out at rest - and then the 80-100bar pressure is reached almost immediately - opening the pressure switch.
Au contraire ? - mais non mon amis :
- right - because any sensible residual pressure will still empty out the acc. sphere while car is resting - making for time to recharge the sphere's LHM cavity. If no pressure left at all (completely flat) - the LHM cavity in the sphere won't empty out at rest - and then the 80-100bar pressure is reached almost immediately - opening the pressure switch.
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Chris Nolan
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