(1) Some units may reach this wear limit in
A. W h i l e pressurized check inlet caps,
shorter hours than others depending on
c r o s s drill plugs or cross over lines,
j o b application and operator technique.
b l e e d e r s , piston seals and boots at
Brake lining thickness must be checked
each caliper head assembly for leaks.
at no more than 50 hour intervals.
NOTE: Seals in the master cylinder and brake
5. Check brake disc for excessive wear
heads cannot stand continuous pressure, Do Not
Use Emergency System for Parking Brake. Earlier
a. Minimum thickness is ,450 inch (11.43 mm),
failure can possibly result if used for parking.
wear beyond this limit can cause excessive
b r a k e temperature, thus shortening brake
1. Check oil pressur for proper PSIG.
lining life. May also cause excessive piston
t r a v e l and misalignment resulting in seal
a. Check condition of air supplied for water,
leakage.
sludge, etc.
6 . Check brake system for residual pressure in
system.
2. Check master cylinder fluid level.
a. R e s i d u a l pressure check valve must be re-
a. If make up tanks are not on unit, the fluid
moved or a hole of approximately .029/ 063
reservoir level may require a filling to com-
(.736 to 1.60 mm), drilled through center of
pensate for the self adjusting features of the
residual valve on front and rear master cyl-
disc brake system. On larger machines, it may
inder.
require refilling three times during the lining
life. On smaller machines, one refill is norm-
(1) Maximum residual pressure is 2 PSI to 4
ally required for the duration of lining life
PSI (.14 to .28 kg/cm2).
unless an external leak is evident.
b. If system has excessive residual pressure:
3. Check for leaks in following area:
(1) Foot pedal not releasing properly.
a. Lines and fitting from the master cylinder to
A. Air present at power cluster at all times.
b r a k e head.
(2) Relay valve malfunctioning.
b. Fluid leaks at piston area: Boots originally
have fluid installed in them for lubrication and
A. Air present at power cluster at all times.
storage, drain boot and retest.
(3) M a s t e r c y l i n d e r p i s t o n n o t r e t r a c t i n g
C. Fluid leak from cap area.
properly.
d. Fluid leak from bleeder screws.
A. Scored master cylinder piston or bore.
e. Fluid leak from caliper head cross drill plugs.
B. Dirt blocking by-pass port.
f. Fluid leaks from cracked or broken castings.
C. S e a l swollen blocking port d u e t o
wrong oil.
4. Check for worn out linings.
D. Piston return spring missing or weak.
a. Minimum lining thickness is 1/8 inch (3.175
E. P i s t o n in air chamber not returning
mm), wear beyond this limit can cause leak-
properly.
age.
[2]
