Any work on the hydraulic parts below the car should be carried out with the car safely supported on axle stands or standing over an inspection pit. Never work or allow anybody to work on the car (not even for a small adjustment or even just inspection) when it's only the high setting of the hydraulic system that keeps the car up. Even a slight adjustment of the height control linkages or any other failure can cause the car body to drop many inches and easily crush anybody causing death or very serious injury. This is not a theoretical warning, it has already happened. Even with the car safely supported, always watch out for the possible drop in height and allow sufficient room for it to happen.
First of all, take a peek into the LHM reservoir. If the fluid is yellowish, it is old, damp or even diluted with engine oil. If it is dirty, it was probably never ever changed. Proceed to flush the system and renew the LHM.
Start the engine and leave the height in the normal setting. If it takes more than 30 second for the care to rise to the normal height, with the pump working continuously, the pump might be weak or the inlet hose split. If only one end of the car rises, the corresponding height corrector is faulty (often only stuck with dirt or disconnected). If the car rises but falls again, the linkage to the height corrector (or the corrector itself) is suspect. If the STOP light on the dashboard stays on more than 5 seconds after you start the engine, there might be problems with the main accumulator, pressure regulator or the high pressure pump but it is also possible that the LHM level is simply too low.
If the car rose normally but later the pressure regulator cuts in (this is the characteristic clicking at the front of the car) more often than once in every 20-25 seconds, the main accumulator or other components are suspect.
If everything was OK so far, look into the reservoir once more, with the engine running. If you see any significant amount of LHM returning to the container, the steering or the brake compensator valve is likely to leak. Small amounts of returning LHM indicate possible problems with the pressure regulator or the main accumulator.
Turn the steering wheel from side to side (on models with power steering). if the pump runs continuously while you do so, the main accumulator or the front spheres are suspect. The power assisted steering need copious amounts of LHM, so any deficiency in the supply will be instantly obvious when trying to turn the wheel. But if the heavy steering occurs with the car rising all right, the flow distributor is probably clogged. Without the car properly raising, however, the same heavy steering points to the high pressure pump (or its drivebelt slipping). The condition of the main accumulator does not influence the operation of the power steering.
Visit all four corners of the car: press down the corner and release it. If it feels solid without any bouncing, the sphere in that corner is flat. If it is soft but bounces a lot, the shock absorver valve is worn. The correct behavior is soft but with damped bouncing. Sit on the front bumper: the front must sink immediately and rise back to normal height in 10 to 20 seconds. Get off the bumper: the front will jump higher but return to normal in a while. Repeat the test at the back as well. If it does not behave as described, check the height correctors or their linkage. As the correctors are beneath the car and even slightly moving them can cause the car to drop in an instant, it is absolutely imperative to do this (and any other suspension work under the car) with the car very safely supported on axle stands, car lifter or ramps. Make sure that nobody, especially children, can sit into the car while you are working under it (it is best to lock the doors).
Set the height lever in the cabin to the lowest position. The car will sink but it if clonks at the end of the travel, the stops are worn. Then set the lever to maximum, if it takes more than 20 seconds to reach the high level, you can suspect the pump or bad setting of the height corrector—but first, check that there is enough LHM in the system. If the pump works with a loud rattling noise, this might also indicate the insufficient level of LHM.
Fast sinking of the rear end
The LHM returns to the reservoir via the brake distributor valve. If that cannot keep the pressure in the rear suspension but lets the fluid return, the rear end will sink fast. This is not a problem in itself: if the car sits up fast when started, has no other suspension or braking problems, there is no need to rush to the workshop.
There are quite a few other factors influencing the sinking as well. Flat rear spheres, old LHM and hot weather also make it sink faster.
Creaking front suspension
The front struts have a rubber seal around the piston, and when the piston gets dry, the rubber grips it a little. Put the suspension up to full height, lock the steering one way (then the other for the other side). On the piston, there is a rubber protection gaiter. Lift this up and apply a small amount of penetrating oil or LHM liquid to the shiny arm.
Stiff power steering
Check the level of the LHM, clean the filters in the reservoir and renew the fluid if necessary. If the filters were very dirty, you should flush the system. If this does not help, you can suspect some failure in the hydraulics like a flat accumulator sphere, faulty pressure regulator, or even a faulty hydraulic pump.
The system is designed to maintain safety: if the pressure drops, the steering goes first, then the suspension so that you still have brakes until the last drops of LHM. And as the steering requires copious amounts of pressure, even a slight pressure drop might make the steering stiff or default to mechanical instead of power steering. This signals an ongoing deterioration of one of the components involved, so if the stiffness cannot be eliminated by simple cleaning, you'll have to replace some parts sooner or later anyhow.
Wobbling steering wheel
There is a hard rubber bush at the bottom end of the upper steering column, just above the universal joint. If the upper shaft is not correctly adjusted, this bush can work itself out of the column. When it becomes loose, the whole upper shaft and the steering wheel itself will wobble.
To gain access, remove the lower steering column cover. Loosen the bolt of the universal joint and turn the ignition key from the locked position. The upper shaft with the rubber bush can be pushed back into the column, possibly by tapping it slightly with a hammer. If you remove the column (by removing four nuts and disconnecting the connectors of the stalk switches), it might prove easier to drive the shaft and bush back into position. After driving it back, fasten the universal joint.
If the upper shaft is correctly adjusted, the bush will remain in its proper place, hence, if you had to put it back, your steering wheel was set too close to the dashboard. There should be about 4-5 mm clearance between the steering wheel and the upper cover. If it is significantly less than that, especially if the wheel scrapes the cover when turning, the bush will pop out of its place in due time.
Clanking steering wheel
A standard cause on older cars is the flexible coupling between the lower steering column shaft and the steering unit. This is a rubber disk (so-called Hardy disk) fortified with metal. Check it at least once a year to prevent the failure of the steering system which could be, needless to say, very dangerous. The coupling can be seen from the engine compartment, down behind the engine, just in front of the bulkhead, where the steering column shaft enters the engine compartment.
It's easier to replace it with an inspection pit or car lift, however, it can be solved with the car jacked and supported safely on axle stands.
Remove the nut (12 mm) and bolt (5 mm Allen) securing the flexible disk to the axle of the steering pinion. To do that turn the steering wheel to a position where the head of the bolt becomes accessible (ask an assistant to turn the wheel while you observe the coupling). There might not be enough room to keep the nut from turning with a normal spanner but a socket or box spanner might do the job.
Withdraw the bolt completely, otherwise you can't remove the disk. Remove the steering column lower shroud inside the car. Remove the top bolt of the steering column universal joint and loosen but don't remove the lower one. Pull back the rubber gaiter under the throttle pedal. Watch out for the stop light wires.
Pull the lower steering column together with the flexible coupling into the cabin. Take care not to use force if it's stuck, or you can damage the sensitive and expensive servo control valve. Once you have the coupling in your hands, just remove the connecting bolts, and replace the new coupling. Before tightening the nuts check that the steering wheel spoke points downwards when the wheels are in the straight-ahead position.
The main task of the main accumulator (a sphere in front of the engine, similar to the other four; look down between the engine and the radiator) is to maintain the normal pressure in the system. The hydraulic fluid is drawn from the reservoir by a pump operating continuously. The accumulator sphere maintains the pressure for some time but it drops slowly as you use the brakes or the power steering. Once it drops below a minimum level, the pressure regulator (a valve the accumulator sphere is mounted on) opens and lets some fluid enter the accumulator, then closes again as soon as the necessary pressure is restored. The ticking sound comes from the operation of this pressure regulator. As this main sphere becomes old, its ability to retain the pressure reduces and the pressure regulator must open more and more frequently to restore the lost pressure, up to a point when it is nearly always functioning (every 1-2 seconds). Apart from the bothering noise, this puts a heavy strain on the hydraulic pump itself.
If the residual pressure in the accumulator is not yet below a minimum level, it can be refilled, otherwise you have to replace it with a new or reconditioned unit.
But even if the main accumulator is healthy, the system might tick frequently. The cut-in and cut-out pressure of the pressure regulator might be out of tune. Check if a lot of fluid is coming from any of the return pipes on top of the reservoir, especially the thick one from the regulator—this would point to a faulty regulator. Any other failure allowing the fluid to escape from the accumulator and leak back into the LHM reservoir also makes the hydraulics tick fast.
To locate the problem spot more precisely, jack up the car on safety stands and with the engine idling, remove each of the four small diameter return hoses, one at a time, from the reservoir. Have a clean jar and rags ready for LHM spillage. Hose #1 is the one towards the front of the car, #2 comes next, #3 is the right angled hose (do not remove the hose itself, there is a little ball inside you would lose, remove the plastic coupling element instead), and #4 is the last one (the remaining two are the high pressure lines, don't remove them!). Note which of them are returning LHM fluid.
|#1||front and rear cylinders|
|#1 but not #3||rear cylinders|
|both #1 and #3||one or both front cylinders|
|#2||safety valve, front/rear height correctors, power steering cylinder
(the safety valve can be tested by removing the hose at the valve itself)
|#3||front cylinders ventilation|
|#4||brake valve (plus operational return, with brake pedal pressed and released)|
The ticking interval should finally return to about one minute (or more) between ticks (engine idling, nobody sitting in the car). However, older cars quite commonly have an increased ticking frequency (5 to 10 seconds between ticks). Although this does signal that some parts of the system are worn, the car may perform well for quite a long time, at most with minor repairs over time.