Evolution: Xantia Hydractive Suspension Regulation - Info

[xantia_v6]

I did fit "known good" electrovalves that were taken from a car I dismantled last year. However...

I fitted another electrovalve this morning, and the problem is fixed.

One point to note is that the front electrovalve on the XM is an interference fit with the subframe as you unscrew it. It comes out OK (but has to be manipulated back around the bracket to fully remove), but you cant restart the thread without risk of cross-threading (especially with the alloy thread and the friction of the solenoid coil). I used a claw hammer to lever the bracket down, bending it by about 1mm, which gave just enough clearance to be able to screw in the electrovalve.

[white exec]

Yes, the front one is all a bit lacking space around it! Found it several times more fiddly than the back end, and that was on a workshop lift.

Great news that it's now working, Mike.
Look forward to the Road Test Report.

[CitroJim]

Yes, the front one is all a bit lacking space around it! Found it several times more fiddly than the back end, and that was on a workshop lift.

The situation is reversed somewhat on a Xantia...

[xantia_v6]

Speaking of which, I now need to track down another pair of valves for my Xantia.

[Mandrake]

Speaking of which, I now need to track down another pair of valves for my Xantia.

Hydractive blocks you mean, to do the same modification ?

You haven't said yet whether you notice any difference, or are you reserving your judgement for now ?

[xantia_v6]

Well I could tell you how good it is, but then you would all want one...

I have only driven the car 1 km since finishing the job, and it felt pretty much the same as usual.

I will report later.

[xantia_v6]

I have still not driven the XM any significant distance since the modification but I have noticed that it sinks a bit faster than it did before. After about 5 days, the front has sunk about 40mm, and the rear by a little less.

I am not surprised by this, as any internal leakage of the electrovalves, which was previously fed by the main accumulator (and thus not externally visible) is now fed by LHM from the suspension struts.

[xantia_v6]

Having now driven the modified XM for a few months, I can thoroughly recommend the upgrade.

The suspension behaviour is more predictable, although not better than a standard setup when it is behaving at its best. Speed bumps can now be ignored with more confidence, but can still provide a surprise if they are large enough to trigger the body movement sensor into triggering firm mode.

The suspension does sink a little faster when the car is parked, but generally stays up for about a week. This may be dependent on the mileage of the valves fitted.

I hope to do the Xantia soon, I think that I have located a suitable pair of valve bodies, just sorting out postage.

[Mandrake]

Having now driven the modified XM for a few months, I can thoroughly recommend the upgrade.

The suspension behaviour is more predictable, although not better than a standard setup when it is behaving at its best. Speed bumps can now be ignored with more confidence, but can still provide a surprise if they are large enough to trigger the body movement sensor into triggering firm mode.

Thanks for getting back with your results - what you describe fits the theory I had perfectly.

As you say, it wouldn't make it ride any better than it would have previously when working at its best, but it would in theory eliminate the intermittent misbehaviour where it doesn't always ride as well as it should due insufficient supply pressure to switch cleanly into soft mode every time and stay there when it should.

If speed humps are absorbed better now with less of a jolt that also agrees with the theory I had that the sudden jolt of a speed hump could cause a pressure spike that pushed the shuttle valve back towards the hard mode - via backfeeding through the electrovalve to the high pressure supply, which would cause the suspension to go suddenly and momentarily hard right in the middle of traversing the bump - which would cause a harsh jolt. In theory that also can't happen with the new design.

As you say, if you go fast enough to trigger the Hydractive system to switch into hard mode on purpose over a speed hump you will still feel a jolt, but if you drive just below that speed you shouldn't.

I'm a bit sad that I won't be able to try this mod myself - the difficulty of sourcing the parts and doing the work is beyond what I can deal with at the moment as I am so over committed time and money wise, and now that I'm driving my Peugeot Ion as the daily driver and hardly using the Xantia I can't justify spending a lot of money and time on the Xantia! When I do hop into the Xantia from the Ion the ride is amazingly smooth, however it still does have its "off days" where the ride becomes a bit harsh as well, and it could well be this exact same issue...

[white exec]

The suspension behaviour is more predictable, although not better than a standard setup when it is behaving at its best. Speed bumps can now be ignored with more confidence, but can still provide a surprise if they are large enough to trigger the body movement sensor into triggering firm mode.

Mike, that mirrors exactly what I've found here, after replacing the two valves on our XM one year and 9400mi ago. The suspension is just wholly more consistent and dependable, without the surprise excursions into Firm that used to happen before the mod.

With speed bumps, there's a simple choice: take them fast, and the body movement sensor will trigger Firm; take them at a reasonable speed, and the car just floats over them in Soft.

About the only thing that has upset things since installation has been the couple times that air obviously got into the system, and caused some rear end crashiness. This was quickly cleared by a couple of Citrobics. Otherwise, everything good.

Simon - I'll go along with your analysis completely. Your original notes on the changed workings of the regulators turned an overlooked Citroen update paper into something really worth pursuing, even though we did it on a car that Citroen didn't have in mind.

None of this would have happened if it hadn't been for Marc's document 'clearout' in June 2016, of course. See page 1 of this thread for the full details.

[GiveMeABreak]

Well, I'm just so glad you guys are getting so much practical benefit from it

[xantia_v6]

I finally took delivery of a pair of the updated valves last week, and have fitted one to the front of my 1997 Xantia.
The job went more or less to plan, the front valve on a Xantia would be dead easy to change (compared to the XM), but you need to remove the LHM tank to get access to the anti-sink valve. This gives a good excuse to change the LHM.

Knowing that I would need a couple of bleed nipples to close the redundant port on the anti-sink valves, I ordered a couple on the internet, unfortunately I did not realise that for this job you need extra long 8mm bleed nipples. I found out after starting the engine with an LHM fountain under the car (after just filling the tank with new LHM).

As a work-around I borrowed the bleed nipple from the other new valve, and will do the rear of the caar after sourcing a pair of correct nipples.
[edit] The longer nipples are quite hard to find on-line, but I think that these would do: http://www.biggred.co.uk/brake-bleed-screw-brb880092

I was able to confirm that the mk1 Xantia V6 has (unlike all other Xantia variants) XM hydractive damper elements at the front.

I was looking at the XM and Xantia dampers, and realised that you can see the difference between them. The centre hole looks to be the same diameter, but the spring diaphragm on the XM damper is noticeably thicker. The XM dampers are marked 4 6 and the Xantia dampers are marked 2 6. My theory is that the first digit is the thickness of the diaphragm (in 0.1 mm) and the second digit is the centre hole size (in 0.1 mm).

I decided to fit the standard Xantia damper (from the new valve) to my car, as it should make the suspension a bit more compliant over bumps. The same change would probably also give softer suspension on an XM.

[elma]

Whats your reasoning for that change Mike.
I'm asking because it seems detrimental to me in theory.
Specifically because your car has 2x the power of most Xantia and bigger brakes.
I would have thought that decreasing the damping would be unwise considering the suspensions already soft and the roll tremendous on a hydractive Xantia.

[xantia_v6]

Citroen reverted to the softer dampers for the mk2 Xantia V6, which is otherwise mechanically identical. When using the power or the brakes, the hydractive valve closes and takes the hydractive dampers out of the circuit anyway.

[white exec]

If stuck, don't forget that a turned down M8 bolt will do the job.

A bench drill and steadied angle grinder would suffice, if lathe not available.
I used a wood lathe chuck and angle grinder, then fine file.

On the digits, the dampers I removed from my acquired Xantia valves are engraved 2 6, and look to have one black steel disk on each side.

An XM rear wheel sphere 0.7mm damper (cut off a sphere) looked like this:

and carries the digits 3 2 .
The damping looks different in each direction (impact and rebound), and the inside-end small disk complicates things, so not sure how to read the digits.

Obviously Citroen needed to be able to recognise these components for production purposes. Maybe the numbers were just codes for the various specs.