Evolution: Xantia Hydractive Suspension Regulation - Info

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by GiveMeABreak »

white exec wrote:Marc, Wiki, no problem. Leave it a couple of weeks in case more edits are needed.
C.
Chris, I've now added this to the XM Section of the Wiki. I've listed it under the 'Hydraulic Suspension' Section - 5.4 Modification: Evolution - Xantia Hydractive Suspension Regulation
You can follow the link here: https://frenchcarforum.co.uk/wiki/Citroen_XM

Let me know if there are any further changes.
Please Don't PM Me For Technical Help

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Thanks, Marc, for moving it across.

Now done a good bit of mixed travel with the 'new' valves in place, and the ride remains exemplary.
Noticed yesterday that the tendency for the back end to gently rise and/or fall (or both) while waiting at traffic lights, especially if held on the footbrake, has disappeared. The car just sits there, level. Quite novel, but not so entertaining for small children in adjacent cars!
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim »

Chris, I'm delighted this is proving to be a lasting improvement :D
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by stovika »

Valve01-low.jpeg
Valve02-low.jpeg
Valve03-low.jpeg
Valve04-low.jpeg
Hello, I was thinking to join the party regarding this upgrade ;)
I have just bought two Xantia units and are preparing to fit these to my XM 2,5 Break -95mod.

- What tool do I use to unscrew the hydractive valve ? Can it be unscrewed as a whole unit ? It is not much space for a flat spanner, hardly 1 mm at the back of the nut.

- Where can one find the O-ring seals, what size and what material are they made from ?

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim »

Welcome Lars :D

You only have half of the Hydractive electrovalve in the block there in the fourth picture...

In the case of the complete valve I use a 16mm socket on the top hexagon by the leakoff spigot and hope it unscrews the whole valve. Fi, however the base stays in the block and the the other half comes apart - as in the fourth picture - I then use a ground down deep 24mm socket. The edges of the socket need to be ground quite thin so the socket will fit.

If the valve separates into two halves when trying to remove it then do not worry but take care to note very carefully the sequence of how the internal components fit. If you don't then I can supply a picture to show how it goes back together.

I do not know the O ring sizes but i do know the larger of the two green ones is the same size as under the hydraulic pump piston covers. The small one is not available as a part but a kit of assorted O rings should provide a suitable one. Just check it is safe for use with LHM.

If the O rings look OK they should be OK to re-use... I've rarely had to replace one.

Hope that helps...
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

Hi Lars, and welcome.

Yes, follow Jim's advice on unscrewing the EV.
I was lucky, and found that the end/top black hex nut unscrewed the complete EV on both old and new valves. If I remember rightly, the two halves of the EV are actually glued together during manufacture, and getting them apart is normally extremely difficult or almost impossible.

You should be able to reuse the original green O-rings, which are unlikely to be damaged.

I guess you are going to reuse your original EVs from the car in the 'new' late-tupe Xantia valves. That's what I did, knowing my own EVs were working fine.

Having done our own 2.5 with this mod last year, I was thinking of doing a "report update", and to be able to report what a good mod this has been. The ride on our '96 2.5 hatch has never been better, and more consistent. It deals with everything except the very worst abrupt 'steps' in road surface much, much better, and the ride on motorways is just sublime.

Keep us informed on how things go.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik »

- What tool do I use to unscrew the hydractive valve ?
Undoing the top hexagon usually allows you to remove the complete electro valve unit. The two halves the unit consists of are indeed glued together, as Chris says. When working on one of those newer hydractive blocks a few months ago when trying to remove the EV from the block it came apart with a bit of force. The other half stayed stuck in the block. I used a punch and a hammer to undo it.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake »

Presumably the punch and hammer destroyed the bottom hex as it is only soft alloy ? I would consider that a last resort to remove a faulty one not a way to remove a good one.

The bottom and top half of the electrovalve are threadlocked internally - as long as the threadlock holds you can undo it via the hex at the top. If it breaks free a face ground socket is needed. A spanner usually won't work on the bottom hex and will just round it off as it is so thin and soft.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik »

Presumably the punch and hammer destroyed the bottom hex as it is only soft alloy ? I would consider that a last resort to remove a faulty one not a way to remove a good one.
Not at all. It was a strike well placed and it just left a small notch :-D
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by stovika »

Thank you very much everybody for wise advice !
I will get back with an update as the project evolves !;)
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 »

Today I fitted the later type of hydractive valve to the rear of my XM. Contrary to Chris's advice I did the job lying on the floor with the car on axle stands. This made things a little more awkward.

One thing that Chris does not seem to have mentioned is that on the XM, the mounting bracket for the rear valve needs to have a corner cut off to allow the bleed nipple on the later valve to fit.

Another point to ponder is the damper elements. The Xantia dampers have different marking to the XM, but for both models the front and rear dampers have the same markings, likewise the front and rear hydractive assemblies (including the dampers) have the same part number. This (surprisingly) seems to indicate that the centre sphere damping is the same front and rear.

If the damping is that un-critical, why do XMs and Xantias need different damper settings? The weight of the cars is not that much different.

This reminds me of another oddity (which I have mentioned before), that the Mk1 Xantia V6 was fitted with XM damper elements at the front, but the Mk2 Xantia V6 reverted to Xantia damper elements. Why? and what difference does it make?
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake »

xantia_v6 wrote: Another point to ponder is the damper elements. The Xantia dampers have different marking to the XM, but for both models the front and rear dampers have the same markings, likewise the front and rear hydractive assemblies (including the dampers) have the same part number. This (surprisingly) seems to indicate that the centre sphere damping is the same front and rear.
Yes that's correct, however keep in mind that the centre spheres never work in isolation like the strut spheres do - the soft mode is centre and strut spheres connected in parallel providing two flow paths for the oil from each strut to take.

So the overall characteristic of the soft mode is an amalgam of strut and centre sphere gas pressures and damper valves. So even though the damper valves in the hydractive blocks front and rear are the same that doesn't mean the damping characteristics are the same in the soft mode front and rear, because the strut spheres differ so much.

Also the gas pressures of the front and rear centre spheres also differ considerably, so the effective damping Q factor is different even for the same damper valve. A lower gas pressure at the rear gives a stiffer springing rate, which will give a higher Q to the damping of the damper valve - however that assumes that the leverage ratio of front and rear rams is the same, which they're probably not - and I haven't sat down to work out the ratios of the front and rear suspension to figure out which way they differ.
If the damping is that un-critical, why do XMs and Xantias need different damper settings? The weight of the cars is not that much different.
I don't think its right to say the damping is uncritical just because the front and rear damper valves are the same - as I described above the tuning front and rear is still different in soft mode. However why XM and Xantia valves differ and in what way I don't know.
This reminds me of another oddity (which I have mentioned before), that the Mk1 Xantia V6 was fitted with XM damper elements at the front, but the Mk2 Xantia V6 reverted to Xantia damper elements. Why? and what difference does it make?

Good question. My Mk1 and Mk2 V6's both rode quite different to each other, even with recently replaced spheres, however in my experience no two models of Hydropneumatic Citroen ride the same even if they are the same model so it's hard to know if it was model related difference like the one you suggest, or just variations in the individual cars!
Last edited by Mandrake on 09 May 2017, 21:49, edited 1 time in total.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec »

You've taken the plunge, Mike!

Looking back at the job, I think that doing the rear valve on stands, or ground ramps, would have been possible, because access isn't too bad once the spare wheel and cover, rear exhaust and heatshield has been got out of the way. The front EV is a different kettle of fish (on an XM, easier on a Xantia) altogether, and needs both good access and a really good view of a tangle of pipework and return pipes in the area. Working by fumble on the front would, I think be hugely frustrating and risky (danger of trapping pipework under support bracket). I'm also, these days, somewhat averse to working lengthily under raised cars. Will never work with just one pair of axle stands: always two pairs, and/or stout ramps. Just a personal thing.

I didn't find I needed to modify the rear bracket on ours; new valve just fitted.

Damping: for XM, both FF and RR centre sphere damping is 1.25, and in the valve body, with no damping in the centre spheres themselves (FF 450/70/--, RR 400/50/--). Not sure offhand what the Xantia damping figure is. Off the top of my head, Xantia offers a tauter ride than XM, which would explain different damper figures. I simply swapped the original XM damper inserts into the 'new' Xantia valves, to preserve characteristics.

Hope the job completes well. Are you going to do the front EV as well?

Eight months on, the ride on ours remains exemplary (with the exception of driving slowly over the proverbial pennies, or viscious edges), and consistently so. What has gone are the random back-end crashes in Firm when taking unexpected humps. High speed travel is extraordinarly good.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake »

white exec wrote: Damping: for XM, both FF and RR centre sphere damping is 1.25, and in the valve body, with no damping in the centre spheres themselves (FF 450/70/--, RR 400/50/--). Not sure offhand what the Xantia damping figure is. Off the top of my head, Xantia offers a tauter ride than XM, which would explain different damper figures. I simply swapped the original XM damper inserts into the 'new' Xantia valves, to preserve characteristics.
The centre sphere damping valves in a Series 1 2 litre petrol Hydractive 2 Xantia (the one I had in NZ) are only 1.1mm. I don't know whether the V6 is the same or differs as the technical data I had at the time did not cover the Series 2 cars or V6.
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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim »

Mandrake wrote:[ however in my experience no two models of Hydropneumatic Citroen ride the same even if they are the same model so it's hard to know if it was model related difference like the one you suggest, or just variations in the individual cars!


That indeed is exactly my experience over the ownership of many...
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