Xantia hard rear suspension

[mills]

I have a xantia 1999 exclusive the rear suspension goes solid when starting the car without operating the hard ride button

After a while it returns to normal soft ride then it will refert back to solid
This is only happenning to the rear only. the front stays normal its just as if the spheres are empty

I have had citroens for 25 years so I know when the spheres are gone

Can anyone help please

Martin

[Homer]

The button does not switch the car from hard to soft. It just makes it switch over at lower speeds/inputs.

But I suspect you have a loose connection. If I remember rightly the system energises to put it in soft and "fails" to hard mode.

[rory_perrett]

I've got something similar on a 1998 Exclusive. On starting in the morning the rear feels hard, not quite as bad as if it is on the top setting but noticeable harder then normal. After a while (up to 5 miles) I can feel the back drop and then its fine. The car was like this when I first got it at 4 years old and 115k miles. I changed the rear spheres but in the process sheared the pipe to the anti-sink sphere. Ended up running the car without the anti sink sphere for a few months and the problem was gone. When I finally got round to replacing the pipe to the anti sink sphere and fitting the new sphere the problem returned. Got me baffled as well!

[np]

I`ll be interested in how this topic goes,as my VSX below has started to do this.Hard/firm on the rear for a while after starting,then it seems to go hard sometimes while driving.I pulled out of a junction tonight onto a up hill road with a few bumps.It felt as if there was no give in the rear suspension at all.I felt every bump,as if the rear was as low down as it would go.But it was at the right height,as i could tell from the headlights.Half a mile later it was riding fine.
I thought that the spheres will need changing,as i`ve had the car 4 yrs next month,put 53k miles on it(towing as well)with no sphere changes.

[Mandrake]

The button does not switch the car from hard to soft. It just makes it switch over at lower speeds/inputs.

But I suspect you have a loose connection. If I remember rightly the system energises to put it in soft and "fails" to hard mode.

Not only this, but when the computer switches the solenoid from hard mode (solenoid off) to soft mode (solenoid energized) it gives a half second burst of full 12 volts to switch the solenoid, after that it drops back to about 3 volts to hold it energized.

The thing about this is 3 volts is NOT enough to switch it to soft, only to maintain soft mode once pulsed to 12 volts.

This means that if for some reason the solenoid drops out in soft mode due to (for example) mechanical vibration causing a momentary loss of power, the solenoid will stay in the hard mode even though the computer thinks its in the soft mode. Depending on how you drive, it may stay in this "falsely hard" mode for some time.

It's not until the computer triggers a soft -> hard and then a hard -> soft change again that it gives the 12 volt pulse necessary to kick the solenoid back into the soft mode.

Can those of you who have this problem of long periods of harsh ride try the following test - simply floor the accelerator pedal quickly, momentarily, then release it back to normal. This will trigger a change from soft to hard and back to soft again, and if the problem is like I describe above the ride should return to normal. (For a time...)

In sport mode even a light tap of the accelerator will do the trick but in comfort mode the accelerator sensor is much less sensitive so you'll have to punch the throttle most of the way to trigger it.

I think my car occasionally has behaviour like this too, as I'm still hunting down intermitant harsh ride, one thing I notice my car sometimes does is when it lifts in the morning the back comes up then the front, then the back drops a few inches (signifying the hydractive valve is only just opening at that point) then the back lifts up again.

It seems that the hydractive valve is not opening as soon or as reliably as it should sometimes, as it normally opens before it starts lifting (noticable as a very tiny drop just before starting to lift) and it only ever happens at the back, never the front.

My suspicion is that there is a mechanical or hydraulic problem in the valve unit (probably just wear, or sludge in the valve from dirty oil) such that even with the solenoid powered it sometimes doesn't actually switch over the valve. (The valve that actually controls hard/soft mode is a slave to the solenoid)

Regards,
Simon

[np]

Can those of you who have this problem of long periods of harsh ride try the following test - simply floor the accelerator pedal quickly, momentarily, then release it back to normal. This will trigger a change from soft to hard and back to soft again, and if the problem is like I describe above the ride should return to normal. (For a time...)

Thats what happend to me yesterday pulling out of the junction.Turning right,uphill,been sitting there for ages waiting,saw a gap,floored it.Hit the rev limit in 1st & 2nd ,thats when it was very hard.Once i eased off when i got up to speed,the car started riding softly again.Although it is riding harder than it used to,hence the need i think to do the spheres.

[Mandrake]

Can those of you who have this problem of long periods of harsh ride try the following test - simply floor the accelerator pedal quickly, momentarily, then release it back to normal. This will trigger a change from soft to hard and back to soft again, and if the problem is like I describe above the ride should return to normal. (For a time...)

Thats what happend to me yesterday pulling out of the junction.Turning right,uphill,been sitting there for ages waiting,saw a gap,floored it.Hit the rev limit in 1st & 2nd ,thats when it was very hard.Once i eased off when i got up to speed,the car started riding softly again.Although it is riding harder than it used to,hence the need i think to do the spheres.

Unfortunately that is normal behaviour, they designed the accelerator pedal sensor to trigger a (couple of seconds) switch to hard mode any time you press or release the pedal rapidly, to prevent the body pitching. It's VERY sensitive in the sport mode, any flick of the pedal will do it, and somewhat less sensitive in comfort mode.

Unfortunately it seems like they decided upon the thresholds based on a manual car, and on an automatic like mine, you pretty much have to punch the throttle any time you pull away from the lights which means a hard ride across the intersection in either comfort or sport mode switch setting.

I got so sick of this behaviour that I've actually disconnected the throttle sensor for now and the around town ride is much better now that its not doing unnecessary switches to hard all the time.

(It will still switch to hard based on speed vs steering wheel angle, eg cornering, braking, and going over large road ripples)

However I feel that the sport mode is now not quite as responsive as it could be, so I've devised a very simple modification (hopefully just a piece of wire, and a couple of diodes, if my idea works) which will allow the throttle sensor to work normally in sport mode, but disable it in comfort mode, by utilizing the sport/comfort switch itself...

Regards,
Simon

[np]

The thing is,it never used to be like this.If it did do it,you certainly could`nt tell any difference.I could always fell a difference after pressing the switch,after a few minits the ride was firmer.Now though,the ride is like it used to be on the sports setting,& when switching to sports mode,its very hard/harsh.On the motorway at any speed,the car wafts along like a good Xantia should,but on normal roads other than glass smooth it rides like a "normal" car.Thats why i thought it was about time to change the spheres,as there was no record of them being done before i got the car,& that was 4 yrs/53k miles ago now.

[Mandrake]

The thing is,it never used to be like this.If it did do it,you certainly could`nt tell any difference.I could always fell a difference after pressing the switch,after a few minits the ride was firmer.Now though,the ride is like it used to be on the sports setting,& when switching to sports mode,its very hard/harsh.On the motorway at any speed,the car wafts along like a good Xantia should,but on normal roads other than glass smooth it rides like a "normal" car.Thats why i thought it was about time to change the spheres,as there was no record of them being done before i got the car,& that was 4 yrs/53k miles ago now.

Ideally you would want to pressure test the spheres, rather than just replacing them blind. (Otherwise you'll never know which ones were low for next time, and possibly waste a lot of money)

If the corner spheres are getting low the hard mode will get much harder but there wont be too much difference in the soft mode.

Also I have noticed that when the front struts are a little bit sticky or dry that the effect is very much like the front corner spheres being flat - very hard and fidgety in the hard mode during cornering.

I was so convinced that my front corner spheres were flat that I got some good condition second hand ones and only noticed a small improvement, still an unusually harsh ride at the front in the hard mode, so later on I got the chance to pressure test my front spheres, as I was suspicious of the second hand ones that I had got.

The result was that the second hand spheres I had obtained were bang on their correct pressure of 45 bars, the old ones that I had thought flat were only down to about 40 bars, and my centre hydractive sphere was 82 bars when it should have been 75, which is even softer than normal. (Someone must have regassed it before I got the car....)

So the spheres were not the cause of the trouble.... lubricating the struts on the other hand made more improvement than changing the spheres from 40 to 45 bars...

The only trouble is I've yet to devise a method of lubricating the struts that gives more than a temporary improvement... (eg days, weeks)

I'm beginning to suspect that when lubrication makes a dramatic but only temporary improvement to the ride, that that is a sign that the strut bushes are worn excessively and probably need replacing for any kind of long term improvement.

Regards,
Simon

[mills]

Thanks for your input

When my suspension goes solid it happens all by it self( I mean solid)
Could it just be the spheres??

Today I travelled 180 miles and four times it went solid and returned to normal after sometime

Martin