Xantia Softer Spheres

[alan s]

Apart from the reasons above, the other thing that needs to be taken into account is that the diameter of the oriface is many times different between HA and non HA suspensions, but apart from that, the actual damper fitted to the end of the sphere which controls to actual up/down ride and I've always been of the opinion that the various gizmos that control the HA suspension will control them, so if the different sphere is taken out of the equation, doesn't that then take these HA controls out of the system rendering the basic part of the HA inoperative?

Pages 32 - 36 could be worth a read to figure if this is the case here:

http://www.tramontana.co.hu/citroen/gui ... cation/pdf



Alan S

[Mandrake]

I agree with your comments Alan. I fitted comfort spheres to a fully working XM VSX, I took them off after less than 5 days....

But...

It does seem to be the case that some, maybe alot of Hydractive Citroens aren't as smooth/comfy as they should be. Out of 3 Citroens, all with Hydractive 2, only one had a floaty ride. The problems on mine seem to manifest themselves as what could be best described as a 'jiggly' ride on non smooth surfaces.

Count me in on that one. I finally got a chance to drive another Hydractive 2 Xantia for the first time recently, and I was struck by the absence of "jigglyness" of the ride at the front on lumpy street surfaces compared to mine, even though I've put a lot of work into mine and the front spheres are all fine.

This other Xantia did have other problems though - rear Hydractive sphere punctured, ride height too high at the front etc which I advised the owner about.

Getting back into my car, the ride was definitely better overall but it was also noticeably jiggly at the front, something you would expect from firm damping.

And I don't even think that someones cheated and fitted standard (instead of Hydractive) spheres at the front, because on a bounce test at the front, mine is softer.

This is after replacing all the spheres, stripping and cleaning the Hydractive blocks and electrovalves, hydroflushing the system, adding diodes to the ECU along with a status LED that can be seen when driving to show the car really is in soft mode and even increasing the system pressure a little to make sure the Hydractive valves do swap over to soft mode. If the car is in hard mode you can tell that the ride is firmer still.

Still trying to sort this, same as many owners by the looks of things.

Don't get me started on that...

Interesting your comment about increasing the system pressure, I remember you talking about doing that some time back - do you think it made a difference ?

I've often thought that the system pressure - which can be as low as 145 bars before the regulator cuts in again, is only marginally high enough to lock the shuttle valve in the Hydractive block in the "soft" mode when you consider that the front suspension pressure with NO PASSENGERS is just over 120 bars. (I've measured it) Add a bit of weight and the front suspension might be right up to 130/140 bars, and there is not enough pressure margin.

The effect would be that the sudden transient pressure increase in the suspension when a bump is hit might actually exceed the static pressure by a considerable margin - causing the shuttle valve to move from its seat and momentarily switch to hard mode for the duration of an individual bump, so that even though the suspension is nominally in "soft" mode when you're bouncing it by hand, it might be briefly in hard mode for individual bumps - hence the jiggly ride on lumpy surfaces, even though the ride is smooth on contoured surfaces.

The Hydractive electrovalve when in soft mode is permanently open from the main system supply to the shuttle valve, and if the transient pressure exceeded the main supply pressure it would backfeed in the direction of the pressure regulator. (Thanks to the accumulator sphere - which gives it somewhere compressible to go)

What would eliminate the possibility of this problem 100% without any tampering with the regulator, would be to insert a tiny one way quick action ball valve in the feed to the electrovalve just where it goes in - no backfeeding possible would mean that the transient pressure could spike well above the regulator pressure but the shuttle valve would remain locked in place.

The only thing thats stopped me trying this already is that I can't find where to get a valve like this - you want something that is pretty small and has (or can be adapted to) have the citroen 2.6mm pipe fittings on it, so you can literally insert it in line just before the Hydractive block, and with the right ones it would be a very simple job to fit them.

Any ideas anyone ? Are there any ball valves like this already in the car somewhere that could be scrounged from a wreck ? Just to cut people off at the pass - no, the security valve is not suitable.

Regards,
Simon

[steelcityuk]

Hi Simon,

It did help the Xantia a little but didn't cure the jigglyness. The Hydractive valves could be heard to cut in with a more definate clunk than before. Maybe a possibility could be to take the cut in pressure to 160 Bar and cut out to 175 Bar. I guess this would mean the pressure regulator would need recharging more often which would put more strain on the pump. Another addition would be to use a front Hydractive sphere (500cc depending on model/date) in place of the standard regulator sphere, a larger reserve of pressure may help the pump if the pressure is upped.

Here's an excellent thread with details of how an XM owner improved the ride by using a different flushing fluid over a long period.

http://club-xm.com/forum2/index.php?showtopic=3072


If you're not a member it would be worth joining just to read the theories George has come up with.

Another interesting thread here -

http://club-xm.com/forum2/index.php?showtopic=3131&st=0

In this thread George comes up with the idea that exercising of the suspension could clean the little used passageways in the Hydractive blocks if it is done with the suspension electronically locked into hard mode. If you read the thread it will explain better.

Nice to hear from you again Simon.

Regards.

Steve.

[MikeT]

Here's an excellent thread with details of how an XM owner improved the ride by using a different flushing fluid over a long period.

http://club-xm.com/forum2/index.php?showtopic=3072

That is absolutely stunning! Both the report and the video demonstration.

But is it true? If it is, then I want some Hydronet 2000 pronto.

[steelcityuk]

I would guess that there's alot to it. Not only the flushing aspect but the general condition of the hydraulic components. Personally I still think that a heated flushing would speed up the process.

Steve.

[DickieG]

Whilst not wishing to put a dampner on this I do wonder how much of this is the 'Placebo effect' as assessing the performance of a car's suspension is rather subjective unless you have another car to the same specification (or computer) to directly compare it against on the same road on the same day etc. Whilst obvious signs such as a sticky strut is easy to spot, ride comfort can be another issue altogether, I wonder, are we chasing rainbow's

[steelcityuk]

Well I can't speak for other peoples Citroens but the White XM I had was far smoother riding than either my current XM or the Xantia Exclusive I had before. Jiggly exactly sums up the ride on some of the roads I drive every day, the same roads driven in the wifes VW Polo aren't jiggly. I think the Club-XM thread show just how much suspension travel a XM should have. In my opinion if you think that a standard sprung car is as comfy as a hydractive Citroen then the Citroen isn't working right. The white XM I had felt floaty when in normal mode, however as soon as the ECU switched over to sport mode the ride was much tighter and the car felt as if it had shrunk to small hatchback size with loads of grip and little body roll. That's what I'm aiming for with my current XM.

Steve.

[MikeT]

I just can't relate to the video though, is it speeded up or something? Is there a forklift out of sight?

[Mandrake]

Whilst not wishing to put a dampner on this I do wonder how much of this is the 'Placebo effect' as assessing the performance of a car's suspension is rather subjective unless you have another car to the same specification (or computer) to directly compare it against on the same road on the same day etc. Whilst obvious signs such as a sticky strut is easy to spot, ride comfort can be another issue altogether, I wonder, are we chasing rainbow's

Good point - there is a certain amount of placebo effect if you only drive the one car...

I was reading the thread and his discoveries about pressure regulator pressures being too low etc, and thinking this guy is onto it, but then he seems to have gone completely off the rails...

He says that the ride was improving after adding the flushing fluid, but that he was doing up to 20-30 Citrerobics sessions PER DAY.... What ??? In my experience with this problem, (assuming my car has the same problem) the ride tends to get better with Citrerobics (but annoyingly, not always, or sometimes it gets worse) and then it gets worse over a few days driving.

So if you're doing that 20-30 times a day, I think that invalidates the results of the flushing fluid - he should be just driving the car normally and seeing what happens.

Secondly, he describes in vivid detail at one point what is CLEARLY faulty, binding front struts - a non anti-sink XM whose front can stay up for hours at exactly the same height, (binding struts) he describes lurching when the car lifts up (binding struts) etc - why doesn't he see that it is binding struts ?

Yes, he might have gradually massaged the struts back into a workable state with 50 gazillion repetitions of Citrerobics, but that seems a bit crazy...why not just fit the replacement struts which he'd already obtained ?

Binding struts will most definitely cause a a very harsh jiggly ride.

But I think those of us that follow this forum who have hunted this jiggly/harsh ride problem have already eliminated the struts - I've actually replaced mine, and while the overall ride is indeed better as the old ones were worn, it hasn't cured the problem.

He has had one day where the ride is super smooth and well controlled (I know exactly what he means) - I've had this super smooth ride effect many times, although I have never quite been able to correlate it with what I've done. Usually it involves depressurizing the suspension though.

I still strongly believe that his original diagnosis was the correct one - that for whatever reason, the Hydractive shuttle valve (not the electrovalve) is not being locked firmly at one end of its travel in the soft mode, and that the jigglyness of the ride comes about from the valve responding to individual bumps, and moving off its stop either partly or completely switching to hard mode during an individual bump. (only during the impact of the bump, not during the rebound - hence the "destabilizing" effect on the ride)

It's probably a combination of low pressure from the main regulator (SOMETIMES, if it is intermittent), sticky shuttle valve, leaking electrovalve etc all having a cumulative effect.

I am surprised though that he made a one way valve for the electrovalve feed and it didn't help - however if he had really badly binding struts at the same time, all bets are off - I'd like to try the one way valves on my car where I know the struts are good.

Another thing that could help diagnose this kind of fault would be a remote pressure sensor - what would be great would be a hydraulic pressure sensor that could be semi-permanently connected to the output of the pressure regulator and a small pressure readout on the dashboard. (with an electrical connection, maybe even wireless, rather than a hydraulic connection to the dashboard...)

That way anyone that has intermittent sometimes good, sometimes bad ride like I do, could immediately correlate it (or not) with low pressure.

Somebody is going to have to start taking drastic diagnostic measures like this to pin this problem down. Any takers ?

Regards,
Simon

(PS I still believe in the air bubbles causing harsh ride theory too - and I don't think they're mutually exclusive)

[aerodynamica]

I just watched George's video. I can see that he's done everything in the universe to get the XM suspension to ride softer however, looking at that I wonder if he has gone a little over the mark. It seems too soft - it's even softer than my CX (and that is running softer than standard) The XM is hitting its lower stops with the weight of one person - isn't that a little too soft?
I must say that the auto self levelling on that XM is up to scratch, so that certainly is a good sign. This is the same as my CX and Xantia, the car relevels after sitting in and after stepping out. The self levelling also affects the ride perception too.

[DickieG]

Having recently obtained an ELIT I plugged into my Activa and VSX to discover that the same fault code was recorded on both cars Hydractive ECU of an intermittant fault on the steering angle sensor. This fault is not viewed as serious by the ECU so any input from the sensor is ignored and the suspension continues to switch between soft and firm modes from a pre-set default. However, I swear blind and still do that the Activa's ride is softer at the front despite what the manual states, the placebo effect?

Some of you may remember that several months ago I bought 'Bernies' Xantia HDi estate from him, a car that he spent many hours of work trying to work out why/whether the ride wasn't always as soft as he thought it could/should be, very much as per the XM described above. Indeed in Bernies desire for a smoother ride he fitted an additional pipe onto the LHM return pipe in the tank in an effort to remove air bubbles in LHM as mentioned by Simon (Mandrake) above, not to mention numerous other investigative work.

As soon as I got Bernies car home I checked the sphere's to discover that the rear ones had been incorrectly supplied and were in fact 'front sphere's', both front wheels were way out of balance and the nearside driveshaft inner joint was worn, needless to say all of which contributed to a loss of ride comfort. Having sorted that lot out a couple of months ago the Hydractive ECU stopped working completely (previously OK) leaving the suspension stuck in firm at all times, not even switching to soft when a door was opened as per the 'anti-jolt' function.

As I had a spare ECU from a 97 Xantia I fitted that to then discover that for the first 2-5 minutes of each journey (by tuning the radio to 171 LW you can hear the Hydractive blocks switching between soft/firm) the suspension would not switch to soft once the cars speed exceeded 15 MPH and would in fact go from soft to firm at 15 MPH and stay there for those first few minutes, after which normal service resumed. Fitting new diodes made no difference. Any ideas as to the cause anyone?

Luckily for me the ELIT arrived just in time before I went mad trying to trace the source of the fault, as it detected that the ECU had registered two faults, again a fault with the steering angle sensor in addition to the brake pressure sensor. Great I thought I'll take a look at the brake sensor, check out the price and (£35) and get a new one. Strangley enough PR.net doesn't list a brake pressure sensor (after RP 7900ish IIRC) and the connection pin for the brake sensor is missing on both the HDi (RP 8382) AND my V6 (RP 7498), both are series 2 models so it appears that Citroën deleted it for series 2 models. The problem I have now is that my series 1 ECU is looking for the brake pressure sensor on a series 2 car where it wasn't fitted so the ECU (as per its default setting) spends a few minutes looking for it the then gives up, puts it down as broken and works from a default setting at the start of each journey. The Hydractive manual states that any fault detected with the brake sensor causes the ECU to work as I describe above.

Now, all new replacement Hydractive 2 ECU's are supplied blank from Citroen and have to be programmed by the dealer as to whether they are being used on an XM or Xantia and once programmed that's it, no second chance. It appears that there is now two versions of Hydractive ECU's for Xantia (apart from Activa's) so what one is fitted to your car? One thing to bear in mind with Hydractive ECU's is that any fault logged on them remains there until it is cleared by a diagnostic tool, disconnecting the ECU from a power source makes NO difference whatsoever, so before you go looking for faults with hydraulic's etc get the ECU read!

I'm quite fortunate here in that I have three Xantia's with Hydractive 2 plus the Activa I can use to compare car's, my VSX has only done 33,000 miles of mainly motorway miles and is still 'as new' inside and out so it makes an excellent point of reference for the other cars and I can confirm that when the ECU is working on the HDi (122,000 miles) its ride comfort is little different from my VSX.

[CitroJim]

That is incredibly interesting Richard

Simon (Mandrake) had a problem with his Brake Pressure Switch in this thread. Lots of useful information on it there too.

I reckon on your MK2 you should be able to fool the ECU by putting a short circuit in place of the switch. Although that begs the question of how the HA ECU knows when to pop the suspension into hard on heavy braking. I guess it does it by calculating the rate of change of speed from the VSS

You could maybe fit a switch. It, I believe, sits in a "K" junction in the front brake feed line under and behined the LHM reservior.

I'm curious now. I was always pretty sure my MK2 Activa had the brake pressure switch. I'll have a closer look when I can but it's not easy to spot.

Have you still got the faulty HA ECU? If you have, I'd like to have a look at it and see if it's repairable. Often, ECU failures are caused by the high power components in them, the darlington drivers similar to the blower regulator transistors. The second and third causes are duff electrolytic capacitors and dry joints.

Did you have a look at the steering angle sensor? It is, I believe, an optical device consisting of a slotted disc with an LED shining through it onto a photocell. Chances are it is full of dust.

[DickieG]

I reckon on your MK2 you should be able to fool the ECU by putting a short circuit in place of the switch. Although that begs the question of how the HA ECU knows when to pop the suspension into hard on heavy braking. I guess it does it by calculating the rate of change of speed from the VSS

IIRC the switch opens at 35 bar hydraulic pressure (maximum braking) and the ECU works the rest out, speed etc.

You could maybe fit a switch. It, I believe, sits in a "K" junction in the front brake feed line under and behind the LHM reservior.

I may simply short the connection at the ECU.

Have you still got the faulty HA ECU? If you have, I'd like to have a look at it and see if it's repairable. Often, ECU failures are caused by the high power components in them, the darlington drivers similar to the blower regulator transistors. The second and third causes are duff electrolytic capacitors and dry joints.

Yes I still have the duff ECU, I opened it up to discover it was spilling out green fluid from the circuit board, with signs of scorching on the two large large components at the top right corner of the board, as per the marked components on page three of the following link http://activaclubfrance.free.fr/Entreti ... liques.pdf (Activa's have a third one here for the third/balancing Hydractive block) Any idea what the component is called? Can they be bought from Maplins?

Did you have a look at the steering angle sensor? It is, I believe, an optical device consisting of a slotted disc with an LED shining through it onto a photocell. Chances are it is full of dust.

I haven't had time yet, I wonder whether the faults are logged when the steering wheel has been removed (it has been on all three cars). Having reset the ECU's they only fault that has re-occurred is the brake sensor on the HDi.

[xantia_v6]

I may simply short the connection at the ECU.

Usually the ECU will be expecting at least one change of state occassionally, or it might decide that the switch has failed in the shorted state,

Have you still got the faulty HA ECU? If you have, I'd like to have a look at it and see if it's repairable. Often, ECU failures are caused by the high power components in them, the darlington drivers similar to the blower regulator transistors. The second and third causes are duff electrolytic capacitors and dry joints.

Yes I still have the duff ECU, I opened it up to discover it was spilling out green fluid from the circuit board, with signs of scorching on the two large large components at the top right corner of the board, as per the marked components on page three of the following link http://activaclubfrance.free.fr/Entreti ... liques.pdf (Activa's have a third one here for the third/balancing Hydractive block) Any idea what the component is called? Can they be bought from Maplins?

Probably not from Maplins, but they can almost surely be bought. It is likely to be a Power FET switching module, but without knowing the part number, I can only guess as to the actual specification. These should be internally protected against overheating, but maybe they were stressed during earlier work on the system. It is also possible that they are a casualty of an upstream fauilure that has killed the pulse width modulation that is their primary protection agains excessive loading.

[CitroJim]

The devices are Solid-State Relays type VN05N and they are available.

What worries me more Richard is this green fluid. Where abouts on the board is that? Up in the left-hand corner in the vicinity of that group of electrolytic capacitors?

There is also a thread here on the Club-XM forum dealing with these devices.

It strikes me that an HA computer is too valuable not to have a go at repairing. It should be fairly reasonable to basically bench-test it as well before tring it for real. An interesting project...