Modification: Evolution - Xantia Hydractive Suspention Regulation

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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.

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.

The 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

Xantia Modified Suspension Regulator.jpg

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 Tool Needed.jpg

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.

Damper inserts.jpg

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.

Damper inserts 2.jpg

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!


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 1210 06 – NFP). An available alternative seems to be 4428 13 (XM front brake, and lots of other cars from AX to Cactus.

Alternatively, use an aftermarket spare, or fabricate from an M8 bolt, as follows:


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.

Real thanks are due to Marc (GiveMeABreak) who made the original post on FCF: containing a link to the Citroen technical document:!Os1j0KxD!prRXUQaII0awVbufykfAW-kAvgEUbKYJMYWzdfc4Qdo.

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.