REPAIR AND TESTING PROCEDURE
OF CALIPER BRAKE HEAD
d. Install previously inspected, repaired, or new
piston in housing.
a. Check for pitting or chipping of chrome sur-
(1) Do not use any force as it is possible to
faces. Light polishing is permissible. Original
cut or nick piston seal when installing pis-
piston dimensions are 2.870/2.873 inches
ton. Rotate piston as inserted.
(72.898 to 72.974 mm).
e. Install piston boot in piston.
2. Inspect caliper head.
f. Install cap seals.
a. Check piston seal groove for nicks or chipped
land areas of seal ring.
(1) Seal chamfers must be on outside diam-
eter side without seal twist.
(1) Internally ported head seal groove maxi-
mum diameter is 3.252 inches (82.60 mm).
(2) Torque bolts to 38-42 ft. lbs. (5.24 to 5.7
Maximum seal groove width is .141 inch
kg/m) dry threads.
b. Check piston bore for diameter, original is
INSPECTION AFTER ASSEMBLY
2.875 inches (73.025 mm).
1. Repaired head should be pressure tested.
(1) Maximum piston bore wear diameter is
2.877 inches (73.075 mm).
a. On machine testing-should be made before
wheels are installed and after properly bleed-
c. Check cross pipe plugs for leaks.
(1) If leakage occurs, replace with ESNA
(1) Insure proper air pressure.
(2) Apply brakes and hold for several minutes.
d. Inspect piston cap seals area for imperfec-
tions or wear.
A. Check inlet caps, cross drill plugs, or
cross over lines, bleeders, and piston
e. Check bleeder and cross tube fitting and
seals, and boots at each caliper head
assembly for leaks.
f. Heat disassembled head, preferably with
steam and inspect visually or use a commer-
b. Off machine testing-must use lining carriers,
cially available spot check solution to check
disc or ½ inch (12.7 mm) spacer plate be-
tween lining carriers.
(1) If magneflux is available, it will also do a
(1) Hook-up Port-a-Power or other suitable
power supply with gate valve and pres-
sure gauge capable of withstanding 1500
PSI (105 kg/cm ).
3. Repair procedure.
(2) Fill head with brake fluid SAE 70-R3.
a. Lubricate all parts, preferably with Caster Oil
or SAE 70-R3 heavy duty brake fluid.
(3) Bleed system completely.
b. Replace piston seals, insuring new seal has
(4) Apply 1500 PSI (105 kg/cm ) maximum
orange dot designating high-temperature
pressure to head, close gate valve and
allow head to be pressurized several
c. Install piston boot in head.