Evolution: Xantia Hydractive Suspension Regulation - Info

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Jan-hendrik » 12 Oct 2016, 12:47

Fantastic, Chris! Now who is going to follow in your footsteps?

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 » 12 Oct 2016, 12:52

I now need to find 2 pairs of late Xantia electro valves...

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake » 12 Oct 2016, 13:01

white exec wrote: Well, it's better. Extended speed bumps (raised pedestrian crossings, two or three metres in length, and maybe 12cm high) can be taken somewhat faster, and without the system annoyingly going firm while negotiating them. I say "going firm", but this was previously not normally shown by the EV LEDs extinguishing. In other words, the EVs remained energised (Soft), but the ride told you different.
I may need to hook an LED up again to see what's happening with mine, because I could swear that my front suspension is going into "hard mode" which it should not, and quite often. The symptom is that I'll be driving down the road and notice that the car seems to fidget side to side in the roll axis over what seem to be fairly inoffensive undulations on a familiar piece of road, also a front wheel will crash heavily into any recessed pothole (tilting the whole car on the roll axis) as if the front is stuck in hard mode and is thus very stiff in the roll axis.

If one end of the car like the front is stuck in hard mode and the other end of the car is still in soft mode it will cause the car to rock and fidget in the roll axis because the stiff end of the car traversing sideways undulations (or independent bumps) will rotate the car on the roll axis with little resistance from the other end of the car due to it still being in soft. If both ends are in soft mode or both ends are in hard mode the car as a whole is balanced for roll resistance so you won't get fidgeting, only if one is soft and the other is hard will you get bad fidgeting...

Sometimes if I flick the throttle a couple of times (to initiate a soft to hard to soft transition) it will come right, other times it won't.

Like you I'm sure that the electrovalve is still energised and thus being command into the soft mode by the computer, but the actual valve in the hydractive control block is not obeying what the electrovalve is telling it, and is either stuck in hard mode, or moves into hard mode during a bump impact due to the pressure spike.

This is exactly what Simon identified in his excellent analysis of the new-type valves - that they should, theoretically, be more immune to system pressure fluctuations and ridge-induced shock-waves, because the regulator shuttle valve is held in position by internal sphere pressure and the new spring, and not by line system pressure. All I can say is, this seems to be so. Unless the car is driven deliberately fast over a raised and elongated hump (when there will be a thump), at decent speeds the car just takes it in its stride, with no crashiness or thump, and, most pleasing, no crash when the back wheels clear the obstacle, just a soft descent. Bingo!
Well, its held in the soft mode by the spring alone - the same hydraulic pressure from the centre sphere is applied to both ends of the shaft, and so in theory should be completely immune not only to supply pressure changes (since line supply pressure isn't used directly at all) but also pressure spikes induced by hitting bumps, because the instantaneous pressure increase will be applied equally at both ends of the control shaft for no net reaction.

For years I've speculated that a lot of the intermittent harsh ride some Xantia's have trouble with is either air bubbles (which definitely does cause a harsh ride) or the hydractive control block either sticking in hard mode long term (eg for seconds or tens of seconds at a time - which mine definitely seems to be doing at the front) or abruptly switching into hard mode part way through cresting a bump, the latter of which would cause a harsh shock.

What you say about speed bumps does ring true - I notice hump backed speed bumps can be passed at a certain speed without any harshness but you only have to go slightly faster and they will hit harshly even though the car has not in fact switched into soft mode electrically. (That takes considerably faster speeds depending on the size of the hump) My theory is that is the valve is being slammed into the hard position mid bump due to the abrupt pressure spike and an inability of the main line pressure to the electrovalve to resist the movement of the valve. The new valve design should be completely immune to this.

Then back up the 8km of mountain road to our village - all good - and again on to the 1km of rocky dirt track. This last was handled far better than the outward journey, with the suspension nicely mopping up the rocky knobbles. Air-in-system presumably gone, and everything warmed up.

So, it's looking good. Worth the effort of changing over? Yes. It was good before, but now it's subtly better, and that's welcome.

What I will do is put together a technical write-up about fitting the replacement valves. There are a few dodges and cautions, and a good bit was learned along the way.
There's one thing you haven't checked yet - leave the car parked over night then in the morning come out and try to bounce the rear and front to confirm that they are both hard, then open a door without starting the engine then repeat the bounce test.

On the old style valves after such a long rest period both ends would be stuck in hard mode due to lack of system pressure until the engine is run - on the new style valves both ends should instantly and reliably go to soft mode and stay there when you open the door, with no assistance from the engine. And they should be able to go back and forth between soft and hard when you close the door for a while and open it again all without running the engine.

I always thought the "anti-jolt" system (what Citroen calls switching to soft mode when you open a door while the engine is off) was a waste of time because it would never work after the car has sat for a while, with the new valve design it should actually work as advertised!

Another problem I used to see a lot on both my previous Xantia's (and this one does it now and then too) is that I'd start the car in the morning, wait for the suspension to rise, then any time between about 5 seconds and 30 seconds later you'd hear a thump and the rear would drop a few inches then pump itself back up. This is caused by the rear hydractive block valve sticking in the hard position for some unknown reason even though the electrovalve is energised. Eventually it lets go and jumps into the soft position. Obviously if this happens during driving it would cause the ride to be hard and fidgety at the rear.

I'm pretty sure that these new style valves would not have this problem. Now all I have to do is get my hands on a pair of these valves for myself... :twisted: I'm very unlikely to be able to do the work until the spring though, as this time of year is batten down the hatches time for me when it comes to major car work! But I'll be on the lookout for a good pair though, as they will be few and far between I'd imagine.

Looking forward to your detailed how-to write up, even if some of it might not be applicable to a Xantia.

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim » 12 Oct 2016, 13:24

Chris, that's excellent and very good to hear :D I now foresee a big demand for late Xantia Hydractive blocks!

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake » 12 Oct 2016, 13:29

CitroJim wrote:Chris, that's excellent and very good to hear :D I now foresee a big demand for late Xantia Hydractive blocks!
Damn it! I should have kept my theory to myself until I had quietly acquired a pair of valves of my own. :-D

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim » 12 Oct 2016, 13:52

Mandrake wrote:
CitroJim wrote:Chris, that's excellent and very good to hear :D I now foresee a big demand for late Xantia Hydractive blocks!
Damn it! I should have kept my theory to myself until I had quietly acquired a pair of valves of my own. :-D
:rofl2:

I have great empathy...

I'm feeling like that about a lot of 1.9TD and S2 Xantia parts I let go Simon... Never thinking I'd have another S2 Xantia or another 1.9TD Xantia...

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec » 12 Oct 2016, 14:08

At least they're not difficult to get at and remove on the Xantia. The scrapyard here pulled them off for me quite quickly - snipped off the 3.5mm pipes, unscrewed the 10mm ones, unplugged the EVs, and took out the three long mounting bolts. Good grief, though, were those Xantias (I looked at three) rusty under there, especially the pipework!

Just go hunting using the RP number, and look for the tell-tale round (or flatted) spring-covering big plug without a torx recess in it, or the added bleed screw. (I did come across an anti-sink non-Hydractive Xantia in one yard - quite a surprise - all tiny pipes!)

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim » 12 Oct 2016, 14:33

Surprised you found rusty ones in Spain Chris... Or was that here in the UK?

Yes, non-hydractive Xantias are very simple hydraulically - relatively :D

The non-hydractive anti-sink ones are even simpler than the sinkers as they have no FDV...

My 1.9TD is simpler still as it has no ABS even...

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec » 12 Oct 2016, 14:52

The cars were here in a Malaga scrappie, but could have come from anywhere. Registration plates lost their regional info from the end of 1999. On a new car, you just get the next one off the national computer - unless you happen to be a police car. In the north of Spain, it can be wetter than the Dordoigne or Britanny. On the Xantias, it was the pipework that looked most sorry.

Buying underbody or cavity wax here is good fun: you can get some funny looks. Then they realise they do have it on their system, it's just that no-one buys it! Wurth, one of the larger manufacturers of it, actually denied making the stuff at all, until I showed them a printout of their catalogue page! Response: Not available in Spain.

After decades of seeing cars rust away in the UK, it's just something I won't put up with any more. Give me (almost) any amount of mechanical and electrical misbehaviour, and I'll get stuck in. Bodywork and patching up is something else, though.

PS
Actually, it's raining hard here now. First real rain since April. Started this morning, and due to continue until tomorrow midnight, with thunder thrown in. Wet roads and roundabouts great fun, after months of being lightly drizzled with diesel and tyre scuff. Lovely! Glad I got the roadtest done before it rained this morning. :wink:

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by CitroJim » 12 Oct 2016, 14:56

Ahh, and there's us all here thinking all of Spain is very dry and kind to cars... Should have known from watching the Vuelta and seeing the rain during some of the mountain stages in the North of the country...
white exec wrote: Give me (almost) any amount of mechanical and electrical misbehaviour, and I'll get stuck in. Bodywork and patching up is something else, though.
Precisely the same here Chris :)

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec » 13 Oct 2016, 07:53

Mandrake wrote: There's one thing you haven't checked yet - leave the car parked over night then in the morning come out and try to bounce the rear and front to confirm that they are both hard, then open a door without starting the engine then repeat the bounce test.
Just done the test:
Before opening door - firm, both ends
With door open - soft, both ends (less soft at front, but that's to be expected)

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by Mandrake » 13 Oct 2016, 08:05

Nice - a perfect demonstration that supply line pressure is not required to operate the valve - as there won't be any left after standing overnight!

Every time the valve opens and closes in response to the door a tiny amount of oil will be consumed from the suspension circuit so if you did it enough times you would loose a little bit of ride height. But you'd probably have to switch back and forth dozens of times to cause any noticeable drop.

While driving this would be topped up of course.

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by white exec » 14 Oct 2016, 19:59

Citroën revised-type Xantia Hydractive Suspension Regulator Valves

The following is a summary of how a pair of Xantia improved-type Suspension Regulator valves (Hydractive Electrovalve blocks) were fitted to an XM (S2 1996). The information it contains will also apply in large part to Xantia.
It is an essentially very simple exchange of the original valves for the updated ones, but there are a few points to note when doing this.

Real thanks are due to Marc (GiveMeABreak) who made the original post on FCF:
http://www.frenchcarforum.co.uk/forum/v ... 29#p494381
containing a link to the Citroen technical document:
https://mega.nz/#!Os1j0KxD!prRXUQaII0aw ... YWzdfc4Qdo .
Internet Explorer will also open this latter link correctly, even though Google/Chrome appears to struggle.
Additional thanks are also due to Simon (Mandrake) for his detailed and forensic analysis of the new valve's design.

Working document
The Citroen technical document above Evolution: hydractive suspension regulation HYDRACTIVE SUSPENSION is the basis for the operation, and a copy needs to be available and understood, and used in combination with these notes.
The document describes how these regulators (which were fitted to Hydractive Xantia and XM) were redesigned (from RP 8155 onwards) so that the internal hydraulic shuttle valve, which switches between Firm and Soft suspension modes, is more positively held in Soft mode (by a spring), and is more hydraulically balanced by incorporating new ‘internal pipework’.
Xantias from RP 8155 (7 March 1999) onwards were fitted with these new valves as standard. The new valves were also available as service replacements for older vehicles. All these valves are now NFP, and so will have to be sourced from spares vehicles.
Xantia received the revised valves, but XM, being very close to the end of its production run, did not, so far as we know.
The technical paper contains full details, as well as clear diagrams of the previous and new type pipework and valve internals. The valves are suitable for fitting to vehicles with or without SC.MAC (‘anti-sink’), and instructions for both are included in the Citroen technical paper.

Physical compatibility

Image

The new type valve is externally almost identical to the old type, with the exception of the deletion of one the two M8-threaded (3.5mm pipe) ports, and its replacement by an M8 bleed screw. The replacements I sourced (from a 2001 Xantia), did not have the two flats on the new round plug (#15), but were otherwise exactly as illustrated.
The position all other items (sphere mounting, 10mm pipe entry, the three long valve mounting bolts, electrovalve solenoid) remains the same.
The electrovalve solenoid remains unchanged, too, and so if desired, the car’s known-good originals can be moved across into the new valves.

Items needed
2 new type ‘internal pipework’ suspension regulator valves (front and rear valves are identical)
2 additional M8 bleed screws (for blanking off SC.MAC port, or hydraulic union if a ‘sinker’) – see note below

Special tools needed

Image
None, except a good-condition 8mm flare spanner (ring spanner with cut-out to pass over 3.5mm pipe), preferably of hex and not bi-hex design. Several 8mm couplings will need to be undone and refitted, and these spanners will avoid inconvenient damage to the pipe securing union.

Working access
It is necessary to depressurise the hydraulic system before removing the old-type valves and fitting the new. This should involve keeping the vehicle on its wheels, and not letting them hang. Access to both front and rear valves and pipework is fairly good, but this wouldn’t be a job where I would recommend laying on one’s back under the car, however well supported. Access to a flat-bed (wheel-supporting) workshop ramp really is a good idea for what will be at least a full-day job, done carefully.


REMOVAL AND REFITTING

Removal of the existing valves is straightforward, even if fiddly. On XM, the front valve sits on its own bracket, which should be unbolted from the subframe (two pairs of small bolts) with the valve still attached. At the rear, spare wheel/carrier and heatshield need to be removed, and tailpipe exhaust box whipped off.
As each pipe is detached from the valve, plug the threaded hole with either a short M8 bolt (for the 3.5mm pipes), or a piece of clean tissue for the larger ports. Cover exposed pipe ends with tape, to prevent dirt getting in. The electrovalve solenoid can simply be unplugged.
With both new and old valves on the bench, make sure all apertures are plugged to stop dirt ingress, and clean up the outside of each as necessary.

Now you should work REALLY CLEAN...

10mm pipe connections
The Citroen working paper refers to the old ISO hydraulic union, and this being replaced from RP 8053 (25 March 1998) with a new CITROEN hydraulic union. The difference between the two is that the first type had a bell end to the 10mm pipe, while the second type featured a brass-and-rubber olive to make the 10mm pipe seal.
(The Citroen paper refers to notches on the new-type CITROEN unions; in practice, I found notches on both old and new unions.)
The new ‘internal pipework’ valves you have sourced could be of either type, but if you are going to fit a second type valve to earlier (ISO) 10mm pipework, or vice-versa, all that is necessary is to remove the large threaded unions (#14 in the diagram above) from your original valves, and screw them into the new ones. (The threads, internal and external, are identical, but the internal drilling is of a different depth and profile.)
And, while the large unions are being taken out . . .

Swap over the damper inserts
Removing the large unions will expose the damper inserts, with their tiny central drilling and by-pass washers. There will be a small 2-digit number engraved on the outward-facing side of each damper, either side of the central hole.

Image

To preserve the damping characteristics of the vehicle, take the dampers from your original valves, and install them in the new. They will in all probability have different numbers on them.
Important note:
Although the valve bodies (old and new) are identical for front and rear, the damper elements contained will be specific to each end of the car. It is important, then, if working on both valves simultaneously, that the front and rear damping elements are not accidentally exchanged. If dealing with only one end of the car at a time, this problem is avoided.

Image
The damper unit will either drop out (when the large union is removed) or may need a gentle rap to allow it to fall out.
Fit the dampers, and replace the appropriate large threaded unions. Note that each has an O-ring fitted, which need not be renewed if handled carefully.

Round/shouldered side plug
It is not necessary for this to be removed, but if it is it will give access to the spring (about 20mm long, and surprisingly stiff) that presses down on the slide-valve end, thus biasing it to Soft mode. There is a nylon insert in there too, to be got the right way round.

Electrovalve solenoids
These are the same for both original and revised regulator valves. The aluminium solenoid body (with an outer coil assembly/connector, which should be able to swivel on the solenoid body) will unscrew from the main valve body on its very fine thread. Note the O-rings.
You may wish to exchange your original (known good) solenoids for those present on the recovered Xantia items.
If testing these EV solenoids, be sure to only connect correct polarity to avoid damaging the internal protection diodes. The polarity is marked (+ and -) on the brown solenoid plug. There is a recommended safe testing procedure, which should be followed. Do not simply connect to 12v.

Old (OE) regulator valves
It might be a good idea to assemble the unwanted parts (unions, dampers, electrovalves...) into the OE valve bodies, in case the conversion needs to be reversed, for any reason. This also will keep the items clean and protected. Do attach a label, in case you forget all about what the hotch-potch actually contains!

Pipework
Before re-installing the new valve, check out the 3.5mm supply pipe that is now surplus to requirements (see Citroen paper). This is the pipe that previously connected the suspension regulator valve to the SC.MAC (anti-sink) valve* at its 3-way end, and is numbered 6 (6a, 6b) in the diagrams. (* See note below Fig.7 in Citroen’s paper for non-anti-sink cars.)
Note: On the SC.MAC (anti-sink) valve, two of the connection ports are exactly opposite each other, with a third close by on the valve end. All three of these ports are connected together internally, and the pipe (6, 6a, 6b) which connects to the suspension regulator valve – and is now redundant – might be connected to any one of these three ports, as dictated by original ease of build.
Carefully identify the redundant pipe, and unscrew it from the anti-sink valve.
Then plug-off the redundant port with an M8 bleed screw (see note below), and tape up (or stopper off) both ends of the redundant pipe. Leave and secure in place, in case needed again (hopefully not).

M8 bleed screws for plugging redundant ports
The 25mm long M8 bleed screws Citroen recommend for plugging the redundant ports are pretty common items. They are the same as the ones already fitted into the new type suspension regulators, and also appear as Rear Brake bleed screws on BX, C25, XM and Xantia (as pt.no. 1210 06 – NFP). An available alternative seems to be 4428 13 (XM front brake, and lots of other cars from AX to Cactus. Note that the thread is standard 8mm x 1.25 pitch (not metric fine 1mm pitch).
Alternatively, use an aftermarket spare, or fabricate from an M8 bolt, as follows:

Image
In this application, it only has to plug, not bleed.

Refitting the new complete valve
Remove any small temporary plugs or plugging bolts from the valve ports, and make sure the old small tubular pipe seal has been hooked out and discarded, and the threaded ports are free from dirt or remnants of rubber. Alternatively, replace the plugs after cleaning, and finally remove them when the valve is back in place, if space allows.
On Xantia, the refit looks straightforward, although I haven’t done this myself. The scrapyard had no problem getting them off.
On XM front, having secured the valve back on to its supporting bracket with the three long bolts, be very careful not to trap any pipework (especially the front Height Corrector 4mm plastic spill-back pipe) between the support bracket and the subframe. Make sure the support bracket front edge is placed properly under the pipework, not on top of it, before bolting down. Check twice, and then again.
Refit pipework, using new seals for the 3.5mm pipes. Be careful to line the pipes up straight with their ports, or the small pipe end will not engage to full depth, and the securing bolt will be difficult to screw in. Beware cross-threading: a steel bolt in an aluminium port is not a forgiving combination! It’s fiddly work, but ok if you line things up, having probably needed to bend the pipework slightly to dismantle it.
Clean up the electrovalve contacts, and refit the plug.
Refit the Hydractive sphere.

Top-up and test
Being cautious, I did one end of the car at a time. I did the rear end first, old valve off, and new valve on. Checked that that worked (bounce test, to check Firm and Soft), and only then, with no problems found, went to work on the front.

Testing and road testing
Top up the LHM fluid, tighten the de-pressurising bolt, start the engine, and check for leaks. Set height control to Normal, and check that body rises – this may be a bit sluggish, because of air in the system, and valves and pipework that need to fill and become properly active. Try a few Citrobics, and check that system is working, and again that there are no leaks. Movement could be somewhat delayed and jerky to start with, as air purges from the system. Check steering and brakes are properly operational.
Road test is now possible.

Bleeding the hydraulic system
Although everything might now be working well, it is a good idea to bleed the hydraulic system. On XM, this is done by applying continuous light pressure to the brake pedal, and opening up the brake bleed valves one at a time, in the following order: RR, RL, FR, FL. Expect to draw off about 1-litre of LHM from the RR bleed screw, and much less at all the others, before air-free fluid emerges.
On Xantia, follow the recommended procedure.
Check LHM reservoir level.


Hopefully, a successful operation.
Last edited by white exec on 15 Oct 2016, 07:55, edited 6 times in total.

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by GiveMeABreak » 14 Oct 2016, 20:17

Chris, brilliant write up - would you mind if at some point I replicated it to the Wiki, we're hoping to build up resources there, and this is just the sort of thing that we need?

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Re: Evolution: Xantia Hydractive Suspension Regulation - Info

Post by xantia_v6 » 14 Oct 2016, 20:24

I agree, a very clear explanation.

If doing both ends of the car at the same time, you would need to be careful not to interchange the front and rear damper elements.