Chrysler PT Cruiser 2001 Service Manual Supplement page 115

5 - 4 BRAKES
DESCRIPTION AND OPERATION (Continued)
Fig. 4 Power Brake Booster
1 – MOUNTING STUD
2 – PARTS IDENTIFICATION TAG
3 – MASTER CYLINDER MOUNTING STUDS
4 – VACUUM CHECK VALVE
spheric pressure to enter on one side of a diaphragm.
Engine vacuum is always present on the other side.
This difference in pressure forces the output rod of
the power booster out against the primary piston of
the master cylinder. As the pistons in the master cyl-
inder move forward, hydraulic pressure is created in
the brake system.
MASTER CYLINDER
DESCRIPTION
Two different master cylinders are offered on this
vehicle. Vehicles without antilock brakes (ABS) use a
standard compensating-port master cylinder, while
vehicles equipped with ABS use a center-valve design
master cylinder. All applications use a 23.82 mm
(0.937 in.) bore diameter master cylinder. The infor-
mation provided here applies only to the non-ABS
master cylinder. For information on the master cylin-
der used on vehicles with ABS, refer to the Antilock
Brake System section.
The non-ABS master cylinder is a four-outlet
design with two screw-in proportioning valves. One is
attached directly to the right side of the master cyl-
inder housing while the other is attached to the bot-
tom (Fig. 5).
The master cylinder body is an anodized aluminum
casting. It has a machined bore to accept the master
cylinder pistons and also has threaded ports with
seats for hydraulic brake tube connections.
The master cylinder has the brake fluid reservoir
mounted on top of it which gravity feeds brake fluid
to the master cylinder when it is required. The res-
ervoir is made of see-through plastic and it houses
Fig. 5 Non-ABS Master Cylinder
1 – RIGHT FRONT BRAKE TUBE
2 – PROPORTIONING VALVES
3 – LEFT FRONT BRAKE TUBE
4 – LEFT REAR BRAKE TUBE
5 – RIGHT REAR BRAKE TUBE
the brake fluid level switch. A removable brake fluid
level switch is mounted in the left side. Refer to
Brake Fluid Level Switch for additional information
on the switch.
OPERATION
When the brake pedal is pressed, the master cylin-
der primary and secondary pistons apply brake pres-
sure through the proportioning valves and chassis
brake tubes to each brake assembly. The brake fluid
reservoir supplies the brake hydraulic system with
the necessary fluid to operate properly.
The master cylinder's primary outlet ports supply
hydraulic pressure to the right front and left rear
brakes while the secondary outlet ports supply
hydraulic pressure to the left front and right rear
brakes (Fig. 5).
The master cylinder reservoir cap diaphragm is slit
to allow atmospheric pressure to equalize on both
sides of the diaphragm.
BRAKE FLUID LEVEL SWITCH
DESCRIPTION
The brake fluid level switch is located in the left
side of the brake fluid reservoir on the master cylin-
der (Fig. 6). It is clipped into the reservoir. It can be
removed from the reservoir and replaced if necessary.
OPERATION
The purpose of the brake fluid level switch is to
provide the driver with an early warning that the
brake fluid level in the master cylinder reservoir has
dropped below an acceptable level.
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