FAULT DIAGNOSIS
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Before searching for problems, remember these vital preliminaries: check that the correct tyres are fitted; that the tyre pressures are right, with plenty of tread; and that the wheel bearings are properly adjusted.
Kearns also suggests getting the driver's impressions. If the steering's lumpy and won't self-centre then the problem's in the linkage; but if it's just downright noisy then check out the hydraulics first.
Of course not all noises are down to the hydraulics.
Oil feed pipes occasionally rattle Inside a loose clip, or there could be loose road spring mountings, worn shackle pins or slack U-bolts.
If there's nothing obvious, examine the reservoir. If the oil's overflowing or looks blackened it could be a worn-out pump that's allowing engine oil and sump gases to get into the oil flow and pushing the level up. Eventually the pump becomes unusually noisy and the steering will be heavier than normal.
So how do you tell a mechanical fault from a power steering problem?
Kearns' method is simple enough— jack up the front of the vehicle, place a lOmm-thick steel spacer on the lock stop (see above), let the engine tick over then steer onto that lock and listen to the note of the engine.
Don't trap your fingers—and don't hold it on lock for more than a few seconds or you'll damage the pump. Effectively, the spacer stops the steering box's pressure relief valve from working and if the engine beat slows it means that the pump is building up a useful pressure and the box is holding that pressure.
Should the noise be unchanged, a dicky. steering box is possible, or indeed an ailing pump. But Kearns suggests that a mechanical problem is still the most likely reason.
If the steering's pulling to one side, then once again the drill is to jack up the vehicle, run it at tickover and "snatch" the steering wheel onto one lock then release it quickly.
If it continues to steer over, a valve could be sticking Inside the box. But more probably the steering wheel will stop as you release it, which points to faulty steering geometry.