512 Auto Fundamentals
(2758 kPa) for cornering, and up to 1200 psi
(8274 kPa) for parking.
The pump can be mounted as a separate
unit and driven by a belt, or it can be built as
an integral part of the front engine plate and
driven directly by the crankshaft. A few pumps
are driven by an electric motor. Most pumps are
belt driven.
Oil returning from the gearbox enters a res-
ervoir. From the reservoir, the oil fl ows into the
pump intake. The power steering pump can be
a vane, rotor, roller-vane, slipper-vane, or gear-
type pump. These pumps operate in the same
manner as the equivalent pumps in the engine
oiling system and in automatic transmissions
and transaxles. The maximum pump pressure
is about 1000 psi (6895 kPa) on newer vehicles
and over 2000 psi (13 790 kPa) on older vehicles.
Pressure is kept within normal specifications
by a pressure regulator valve. The oil (usually
special power steering fl uid or, on older vehicles,
automatic transmission fl uid) provides the lubri-
cation for the pump and steering mechanism.
Figure 25-27 is an exploded view of a vane-type
power steering pump.
Return
passage
(to reservoir)
Valve
Reservoir
Input shaft
Rotary
control
valve
Section A-A
Section A-A
A
A
A
A
Steering
gearbox
Power cylinder
Power cylinder
(high fluid pressure)
Fluid
passage
from power
cylinder
Return
passage
From pump
From pump
Fluid passage to
power cylinder
B
A
Figure 25-26.
Control valve operation. A—Steering straight ahead.
B—Turning left.
Honda
Pump cover
Roller
Pump vanes
(10 plates)
Pump cam ring
Side plate
O-ring
O-ring
Preload
spring
Oil seal
Pump seal
spacer
Pump housing
Drive shaft
Ball
bearing
Circlip
Pulley
Pulley nut
Spring
Pressure
regulator
valve
O-ring
Flange bolt
Control valve cover
O-ring
Inlet joint
Pump rotor
Flange bolt
O-ring
O-ring
Roller
Flange bolt
Figure 25-27.
Exploded view of a vane-type power steering pump. This pump is supplied with power steering fl uid from a remote
mounted reservoir (not shown). Study the construction. Note that 10 vanes are used.
Honda