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Autopapyrus · Citroën BX (1st generation)
https://autopapyrus.com/guides/citroen/bx/front-suspension-cylinder-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Citroën BX (1st generation): Front Suspension Cylinder Replacement

The BX has no conventional telescopic struts: each front wheel rides on a hydropneumatic suspension. The cylinder with its piston is connected to the suspension arm, and a nitrogen-charged sphere is screwed onto the top of it. This job requires fully depressurizing the system and strict cleanliness. A single grain of dirt entering the circuit can ruin the pump or the pressure regulator.

Difficulty: Hard Time: 3-5 hours Steps: 11 Tools: jack and jack stands, wrench and socket set, strap or chain wrench for the suspension sphere, fluid drain pan, syringe or hose for draining, clean rags, plugs for the lines, new O-rings and seals

Part

  • 🔩 Front suspension cylinder (on the BX the "strut" is a hydraulic cylinder with a piston, working together with a sphere). Kit: complete cylinder or a seal and gasket repair kit, suspension sphere (if it has lost pressure), LHM mineral hydraulic fluid (green), new gaskets and O-rings for the lines

Step by step

11 steps
  1. Park the car on level ground and shut off the engine. Use the ride height lever in the cabin to lower the body to its lowest position. Then release the pressure: loosen the bleed screw on the pressure regulator by 1/2 to 1 turn until fluid stops flowing out. Do not unscrew it completely.
  2. Raise the front of the car with a jack and place jack stands under the structural body mounting points. Never work under a car supported by a jack alone. Remove the front wheel.
  3. Place a drain pan underneath. Clean all connections with a brush and rags. Disconnect the return line and the supply line from the cylinder and the sphere, and plug the ends immediately.
  4. Unscrew the suspension sphere. It is threaded on; use a strap or chain wrench if needed. If the sphere is not releasing pressure (no fluid comes out as you remove it, and it is hard to turn), stop and double-check that the pressure has been fully released.
  5. Disconnect the lower end of the cylinder from the suspension arm according to the layout of your assembly. Remove the cylinder's body mount and take out the cylinder. If the ball joint or driveshaft is in the way, free them first. Otherwise, do not disturb the driveshaft or tie rods unnecessarily.
  6. Inspect the piston and the mounting seat. If the cylinder is being replaced only because of a leak, check the condition of the sphere and the lines: replace a worn sphere together with the cylinder.
  7. Install the new cylinder in reverse order. Lubricate the seals with LHM. Do not use mineral engine oil or DOT-type brake fluid. They are incompatible with the rubber parts of the system.
  8. Screw on the sphere and reconnect the lines using new O-rings. Tighten without excessive force, to the manufacturer's specified torque. Do not apply sealant to the sphere threads.
  9. Top up the LHM in the reservoir to the mark. Close the regulator's bleed screw. Start the engine and let the system build pressure. Raise the body with the ride height lever while watching for leaks.
  10. With the body raised, check the fluid level and top up to the correct level if needed. Check the ride height on the left and right sides; if the car sits unevenly, check the height corrector.
  11. Repeat the job on the other side. It is best to replace cylinders and spheres in pairs so both sides behave the same. Final check: take a test drive, then inspect all connections and pour the leftover LHM into a container for disposal.

Common mistakes and warnings

  • The BX system operates under high pressure (about 150-170 bar). Always release the pressure before disconnecting any lines, otherwise a jet of fluid can cause serious injury. If you have no experience with hydropneumatic suspension or are not sure the pressure has been released, have the work done by a specialist shop. The exact tightening torques for the cylinder mount and lines on your version are not given here; check them against the manufacturer's specifications.