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Jim Grant's Tech Tips
'00
Cadillac STS, Steering Wheel Jerk
Q:
The steering wheel on my ‘00 Cadillac STS turns side
to side when traveling over mildly rough roads, and to a
lesser degree when soft cornering. Dealer mechanics have
not offered a conclusive diagnosis.
- Ken
A:
Not knowing
what has and has not been checked I would first suggest
checking the condition & level of the power steering
pump fluid and that the serpentine that drives the belt
is tight and in good condition, after which the front-end
components should be checked. We’ve seen a good amount
of tie-rod end problems. They seem to wear and loosen prematurely.
A loose or worn tie-rod end can cause a feed back through
the steering wheel. If all the front components are tight
be sure the steering rack is secured tightly. Once again
movement of the steering rack will back feed to the steering
wheel. After the steering rack, the intermediate shaft from
the steering rack to the steering wheel should be checked
for wear. If no external components are found to be loose
or worn then there may be an internal power steering problem,
which takes us back to the power steering pump. Contaminated
power steering fluid can result in undesirable operation
of the power steering rack. Contaminants can cause sticking
valves that turn into worn valves if left un-serviced. The
valve that seems to have the most trouble with contaminants
and wear is the pinion spool valve in the steering rack
itself. This valve is the control gate for fluid pressure
to turn right or left. If this valve is sticking or worn
it can get jumpy when the steering wheel is turned. The
result is a feeling that someone else is playing with the
steering wheel while you’re driving. The bumps in
the road cause feed back through the steering that causes
the spool valve to act up. If it all leads down to the spool
valve being the problem, try having the power steering fluid
flushed. If that doesn’t correct the problem you may
be replacing the power steering rack.
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