Regarded by some as the last "real" Citroën, the XM was not really a great success. Launched in 1989, it was intended as a replacement for the discontinued CX, with many improvements including a very sophisticated electronic control system for the hydraulic suspension called "Hydractive" (although right-hand drive XMs lost the DIRAVI variable fully-powered steering, having an almost conventional DIRASS power-assisted setup). The Hydractive system used sensors in the steering, brakes, suspension, throttle pedal and gearbox to determine the car's speed, acceleration, and road conditions. This then switched an extra pair of suspension spheres (grapefruit-sized metal spheres containing nitrogen that act as both springs and shock absorbers) in or out of circuit, to either allow the car a smooth, supple ride, or a much stiffer ride with reduced roll for better handling in corners. The result — when it worked — was a big car with a smooth "magic carpet" ride, with better handling than many smaller, lighter, sports cars. When it didn't work, it was quite harsh and bumpy, although no worse than any high-performance sports saloon.
Most of the problems stemmed from the sensitive electronics controlling the car's hydraulic system. Although the suspension height setting in the cabin had reverted to a mechanical lever (the CX series 2 had an electric motor, which could prove troublesome if not maintained and was difficult to get at), the Hydractive system used a computer-based electronic control unit to switch the valves on and off. It was a little "ahead of the curve" when the car was launched in 1989, and early versions were unreliable and hard to diagnose. The greatest problems throughout the car were caused by the multipoint earth blocks — one on each inner front wing, one at the back, and one under the dashboard. These tended to corrode (especially the ones under the bonnet), causing all manner of weird intermittent faults. Cutting the plugs off the end, and using screw terminals instead, solves them. The faults themselves range from the suspension sticking in "hard" mode, to ABS failure and bulb failure warnings on the LCD in the dashboard, to the heater not working correctly (the original author's own car used to display "ABS HORS D'UTILISATION" on the LCD display, even though it was set to display in English, if you switched on the headlights, heater blower and heated rear window, then pressed the brake pedal - cleaning the earthing block fixed this). Heater blower ECUs and suspension ECUs fail — it's nearly always the big power output transistor that blows. It is possible to replace it with a cheaply available large power Darlington transistor, as replacement ECUs are prohibitively expensive. Many electronics repair shops will be able to do this for you.
You can pick very highly specified examples of these cars up incredibly cheaply. When you get them, they will quite likely have flat spheres — you may be able to replace these yourself, but an independent Citroën mechanic will probably do this for less than £300 (approximately $300 US), including checking the 150m of hydraulic pipe under the car for leaks and damage. Changing the hydraulic fluid regularly is very important — every two years should be enough. Buy a 5l can for about £25 (approximately $50 US) or so. It's far cheaper to do that than repair the problems caused by dirty, contaminated hydraulic fluid. If it's extremely dirty you can try Hydraflush in it, but be aware that this will show up every tiny leak in the system.
The XM was never officially imported into the US, but a few examples are known to exist. Citroën-specific parts must be sent over from Europe. LHM , the green blood of the hydraulic system is virtually unobtainable in the US, although Bendix make a very similar fluid for aircraft hydraulic systems. Automatic transmission fluid will do if you're desperate, but is really too viscous and can wear out the very finely machined valves.
Enthusiasts consider XMs great cars, often very cheap but with minor problems that you can, despite the apparent complexity, fix yourself. Nearly everything is within the reach of a well-equipped DIY mechanic, and basic servicing (oil change, ignition, etc.) will spring no surprises to anyone who has serviced any car before.
The XM was voted European Car of the Year for 1990.
