Chrysler PT Cruiser 2001 Service Manual Supplement page 1149

19 - 18 STEERING
DESCRIPTION AND OPERATION
POWER STEERING PUMP . . . . . . . . . . . . . . . . . 18
POWER STEERING FLUID RESERVOIR . . . . . . . 19
SERVICE PROCEDURES
POWER STEERING PUMP INITIAL
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
REMOVAL AND INSTALLATION
SERVICE WARNINGS AND CAUTIONS . . . . . . . . 19
POWER STEERING PUMP . . . . . . . . . . . . . . . . . 20
DESCRIPTION AND OPERATION
POWER STEERING PUMP
DESCRIPTION
The hydraulic pressure for operation of the power
steering gear is provided by a belt-driven power
steering pump manufactured by TTA (Fig. 1). The
power steering pump is a constant flow rate and dis-
placement vane-type pump.
Fig. 1 Power Steering Pump
1 – SHAFT
2 – SUPPLY FITTING
3 – PRESSURE FITTING
The power steering pump consists of the power
steering pump internal components and the power
steering pump pulley. The power steering fluid reser-
voir is remotely located on this vehicle.
No repair procedures are to be done on the internal
components of the power steering pump.
POWER STEERING PUMP
TABLE OF CONTENTS
page
POWER STEERING FLUID RESERVOIR . . . . . . . 23
DISASSEMBLY AND ASSEMBLY
POWER STEERING PUMP (PULLEY) . . . . . . . . . 24
SPECIFICATIONS
POWER STEERING PUMP FLOW . . . . . . . . . . . . 25
POWER STEERING FASTENER TORQUE . . . . . . 25
SPECIAL TOOLS
POWER STEERING PUMP . . . . . . . . . . . . . . . . . 25
OPERATION
A belt from the engine crankshaft rotates the
power steering pulley turning the pump shaft. The
shaft connects to a rotor. Rectangular pumping vanes
in the shaft driven rotor move power steering fluid
from the fluid intake to the cam ring pressure cavi-
ties of the power steering pump. As the rotor begins
to turn, centrifugal force throws the vanes against
the inside surface of the cam ring to pickup residual
fluid. This fluid is then forced into the high pressure
area. As more fluid is picked up by the vanes, the
additional fluid is forced into the cavities of the
thrust plate through two crossover holes in the cam
ring and pressure plate. The crossover holes empty
into the high pressure area between the pressure
plate and the housing end cover.
As the high pressure area is filled, fluid flows
under the vanes in the rotor slots, forcing the vanes
to follow the inside surface of the cam ring. As the
vanes reach the restricted area of the cam ring, fluid
is forced out from between the vanes. When excess
fluid flow is generated during high-speed operation, a
regulated amount of fluid returns to the pump intake
side through a flow control valve. The flow control
valve reduces the power required to drive the pump
and holds down temperature buildup.
When steering conditions exceed maximum pres-
sure requirements, such as when the wheels are
turned against the stops, the pressure built up in the
power steering gear exerts pressure on the spring
end of the flow control valve. The high pressure lifts
the relief valve ball from its seat and allows fluid to
flow through a trigger orifice located in the outlet fit-
ting. This reduces pressure on the spring end of the
flow control valve which then opens and allows the
fluid to return to the intake side of the pump. This
action limits maximum pressure output of the pump
to a safe level.
PT
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