BRAKES
9.6
HYDRAULIC BRAKE SYSTEM
OPERATION OVERVIEW
A
B
C
D
E
F
Must be clear
to allow
proper dia-
phragm move-
ment
Compensating port
compensates
for temperature
changes by allow-
ing fluid back to
master cylinder
Move-
able
Brake
Pad G
Typical Hydraulic Brake System
The Polaris disc brake system consists of the
following components or assemblies: brake lever;
master cylinder; hydraulic hose; brake calipers (slave
cylinder); brake pads; and brake discs, which are
secured to the drive line.
When the hand activated brake lever (A) is applied it
contacts piston (B) within the master cylinder. As the
master cylinder piston moves inward it closes a small
opening (compensating port C) within the cylinder and
starts to build pressure within the brake system. As
the pressure within the system is increased, the piston
(D) located in the brake caliper moves outward and
applies pressure to the brake pad. This pad contacts
the brake disc and moves the caliper in its floating
bracket, pulling the stationary side pad into the brake
disc. The resulting friction reduces brake disc and
vehicle speed. As the lever pressure is increased, the
braking affect is also increased.
The friction applied to the brake pads will cause the
pads to wear. As these pads wear, the piston within
the caliper moves further outward and becomes self
adjusting. Fluid from the reservoir fills the additional
area created when the caliper piston moves outward.
Brake fluid level is critical to proper system operation.
Too little fluid will allow air to enter the system and
cause the brakes to feel spongy. Too much fluid could
cause brakes to drag due to fluid expansion.
Located
within
the
master
cylinder
is
the
compensating port (C) which is opened and closed by
the master cylinder piston assembly. The port is open
when the lever is released and the master cylinder
piston is outward.
As the temperature within the
hydraulic system changes, this port compensates for
fluid expansion (heated fluid) or contraction (cooled
fluid). During system service, be sure this port is
open. Due to the high temperatures created within the
system during heavy braking, it is very important that
the master cylinder reservoir have adequate space to
allow for fluid expansion.
Never overfill the
reservoir! Fill to 1/4
- 5/16
(.64 - .80 cm) from top
of the cylinder.
This system also incorporates a diaphragm (E) as part
of the cover gasket; and a vent port (F) located
between the gasket and the cover. The combination
diaphragm and vent allow for the air above the fluid to
equalize pressure as the fluid expands or contracts.
Make sure the vent is open and allowed to function.
If the reservoir is over filled or the diaphragm vent is
plugged the expanding fluid may build pressure in the
brake system leading to brake failure.
When servicing Polaris ATV brake systems, use only
Polaris DOT 3 Brake Fluid (PN 2870990).
WARNING: Once a bottle is opened, use what is
necessary and discard the rest in accordance with
local laws. Do not store or use a partial bottle of brake
fluid. Brake fluid is hygroscopic, meaning it rapidly
absorbs
moisture.
This
causes
the
boiling
temperature of the brake fluid to drop, which can lead
to brake fade and the possible loss of control.
HYDRAULIC
CALIPER BLEEDING
T
his caliper is a single piston design. The caliper
pistons are “T”-shaped, which allows both hand and
foot brake to use the same caliper piston, but remain
separated by seals. The hand brake system applies
hydraulic pressure to both front calipers and only the
outer diameter of the rear caliper pistons.
The
auxiliary (foot) brake applies pressure to the inner
portion of the rear caliper pistons. Because the hand
and foot brake hydraulic systems are separate, there
are also two bleed screws -- one for the outer fluid
chamber (hand brake), and one for the inner fluid
chamber (foot brake).
The basic procedure for
bleeding the brake system is the same as outlined on
page 9.7 - 9.8, however, each system must be bled
separately.
Hydraulic Auxiliary Brake inspection and adjustment
is outlined in Chapter 2 beginning on Page 2.28.
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Summary of Contents for SPORTSMAN 400 2003
Page 1: ...2003 SPORTSMAN 400 500 SERVICE MANUAL PN 9918065 The Way Out ...
Page 5: ......
Page 51: ...MAINTENANCE 2 32 NOTES ...
Page 71: ...ENGINE 3 20 CYLINDER HEAD EXPLODED VIEW EH50PL A EH50PL ...
Page 131: ...BODY STEERING SUSPENSION 5 12 NOTES ...
Page 165: ...CLUTCH 6 34 NOTES ...
Page 193: ...FINAL DRIVE 7 28 NOTES ...
Page 217: ...TRANSMISSION 8 24 NOTES ...
Page 239: ...BRAKES 9 22 ...
Page 274: ...PN 9918065 Printed in USA ...