514 Auto Fundamentals
pressure and vibration between the engine-
mounted pump and the frame-mounted steer-
ing gear. Figure 25-31 shows the routing of
typical power steering hoses. The high-pressure
hose is usually a fi tted hose with steel high-
pressure tubing, attached to the pump and steer-
ing gear with fi ttings. The return hose may be a
low-pressure hose held with hose clamps.
Note
In the event of pump pressure failure,
power steering systems can be operated
manually with somewhat more effort than
required with a conventional manual steering
gear. This is because there is always a
mechanical connection through the gears,
even when no hydraulic pressure is available.
Extra effort is required to move the hydraulic
fl uid in the gearbox, as well as turn the
wheels.
Power Steering Fluids
The fl uid level in the power steering pump
should be checked frequently. Check the level
when the fl uid is at its normal operating tem-
perature. Most pumps have a dipstick for check-
ing the fl uid level, Figure 25-32. Fluid level
should be between the add mark and full mark.
If the fl uid level is low, inspect the entire sys-
tem for leaks. If fl uid must be added, always use
the power steering fl uid recommended for the
system. Most modern vehicles are designed to
use special power steering fl uid, not automatic
transmission fl uid. Always check manufactur-
er’s specifications before adding fl uid.
Electronic Steering Control
Electronic steering control systems are
sometimes used on vehicles equipped with
power steering. These systems reduce power
steering assist at cruising speeds to increase
control and road feel, and increase assist at low
speeds to help with parking. If the electronic
system fails, the power steering system operates
normally.
Electronic steering systems are operated by
a control module or the body control ECM. The
control module relies on inputs from the vehi-
cle speed sensor and a steering wheel rotation
sensor. The control module uses information
on steering wheel movement and vehicle speed
to determine the amount of power steering
assist provided by a fl ow control solenoid. The
fl ow control solenoid is mounted in the high-
pressure side of the power steering system,
usually in the pump output passage. In some
Steering gear housing
High-pressure
hose
Tie rod
end
Valve
body unit
Fluid
reservoir
(remote)
Steering
pump Tubing
Low-
pressure
hose
Power steering
speed sensor
Steering
fluid cooler
Figure 25-31.
Overall view of a power rack-and-pinion steering system showing hose and tubing routing. Note the power steering fl uid
cooler. This is an oil-to-air type cooler.
Honda