Hydraulic Brake System; Operation Overview - Polaris Sportsman 800 EFI 4x4 2012 Service Manual

BRAKES

HYDRAULIC BRAKE SYSTEM

Operation Overview

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
9.8
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 has 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
fail
When servicing Polaris ATV brake systems, use only
Polaris DOT-approved brake fluid.
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
9924864 - 2012-2014 SPORTSMAN 800 / 6X6
© Copyright 2013 Polaris Sales Inc.
WARNING
loss of control.