How it Works: Hydragas Suspension

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Hydragas Suspension

Hydragas Suspension Systems

The Hydragas system of vehicle suspension is similar in structure and operation to the Hydrolastic system in that it is fluid-operated and has a displacer unit on each wheel. The front and rear units are linked for each side of the car. The fluid used is water-based. Each unit consists of an integral spring, using inert gas as the springing medium, and a damper unit. In theory, the units are designed to last the life of the car, but if faults develop it is possible to replace the displacer unit.

Removing Displacer Unit

The Hydragas system is pressurized, and a special machine is required to de-pressurize it. Either find a garage that will de-pressurize the system and let you work on the premises, or have the garage de-pressurize the system and drive the car home carefully and slowly. Disconnect the battery, slacken the wheel nuts, jack up the front of the car and remove the wheels. Support the car on axle stands and chock the rear wheels. Then remove the nut and spring washer used to hold the rebound rubber to the suspension arm, and lift away the rubber.

Next, take off the union nut holding the connecting pipe to the front displacer unit. Finally, lift off the knuckle joint with the spacer and spring to free the displacer unit. This will then lift away from the suspension arm. The displacer unit is too complex for DIY servicing, so you will have to take it to a specialist garage for examination and repair.

Re-fitting The Displacer Unit

Re-fitting the displacer unit is the reverse of removal. There are two points to remember. Pack the displacer unit knuckle joint with a suitable lubricant, this must be a non-solidifying heavy-duty grease. Make sure that the knuckle joint ball pin remains in its socket. If the displacer unit is not at fault, check the front/ rear connecting pipe for blockages before re-fitting the system. Clear any blockages in these pipes by removing and blowing compressed air through them.

Blocked Connecting Pipes

To check the connecting pipe for blockages, remove the other end from the rear unit and blow through the pipe. Any blockages should be cleared by blowing compressed air from a tyre air pump through it. If this fails to clear the pipe, buy and fit a new one. Then re-connect the pipe, displacer unit and system, and re-pressurize the system.
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