20 - 2
Service Brakes
Brake Piston Seal Leakage Test
The following procedure explains how to check if a brake
piston seal is severely damaged/perished or if the seal has a
small cut or nick. The test must only be done when the axle
is COLD.
!
WARNING
Before working on the brake system make sure the
machine is on level ground and chock all four wheels.
BRAK 1-4
!
WARNING
Do not drive the machine with any part of its brake
system disconnected. When the following test has been
completed reconnect all brake pipes and bleed the brake
system using the recommended procedure.
BRAK 2-1
1
Remove and cap brake piston feed pipe
A
.
2
Fill the brake piston housing with JCB Light Hydraulic
Fluid.
3
Check for severe piston seal damage:
a
Install a hand pump fitted with a 0 - 40 bar (0 - 600
lbf/in
2
) pressure gauge to port
B
, as shown at
X.
Note
: The hand pump MUST be filled with JCB Light
Hydraulic Fluid. DO NOT exceed 69bar (1000 lbf/in
2
).
b
Use the hand pump to generate a pressure in the
brake piston housing.
c
If the pressure falls off rapidly, or if no pressure
reading can be obtained, the seal is severely
damaged and needs replacing with a new one.
4
Check for small cuts or nicks in the piston seal:
a
Install an adapter fitted with a piece of clear tube to
the brake piston port
B
, as shown at
Y
.
Note
: The tube must be kept vertical during the test, use
tape to attach the tube to the side of the machine.
b
Fill the tube until approximately three quarters full
with JCB Light Hydraulic Fluid
c
Using a suitable pen, mark the level line of the
brake fluid on the tube, as shown at
C
.
d
After approximately 1/2 hour, check if the level has
dropped below the original marked line, if it has
then check the brake piston seal for slight nicks,
cuts or generally for wear.
Section G
9803/3280
Section G
20 - 2
Issue 1
Service Procedures
159830Y
X
Y
159830X
5
Repeat steps 1 to 4 for the opposite brake piston seal.
6
Reconnect all brake pipes and bleed the brake system.
Refer to
Service Brakes - Bleeding
.
