Question:My power steering feels stiff when I first start
my car, but then feels normal after I've driven the car awhile.
How come?
Answer:This is called "morning sickness" and
has nothing to do with being pregnant. The condition is caused
by wear in the spool valve housing on certain power steering racks
-- notably GM front-wheel drive cars.
When the car is first started, the rack is cold and clearances
in the spool valve are at their greatest. Hydraulic pressure
from the power steering pump leaks past grooves worn in the aluminum
spool valve housing. This causes a loss of pressure and increases
steering effort. The steering feels stiff with little or no power
assist. As the car is driven, the rack warms up. This decreases
the clearances inside the spool valve housing, which reduces the
leakage past the grooves. More pressure goes to where it is supposed
to go and the steering becomes easier as power assist returns.
The "fix" for this condition is to replace the rack
with a new one (preferably with a cast iron spool valve housing)
or a remanufactured rack that has a stainless steel sleeve pressed
into the aluminum housing.
