Maintenance
16K PLUS October 2019 6-11
Air Brake Maintenance - Continued
Slack Adjuster Function Test
If the maximum stroke, with an 85 psi brake application
is less than the distance shown in the chart on page
6-10, the Gunite slack adjuster is functioning properly.
Troubleshooting
1. The Gunite slack adjuster should not require
manual readjustment. If the maximum chamber
stroke is within the range for the size chamber used
(see g. 3), the slack adjuster should not be manually
readjusted. If the chamber stroke exceeds the limit,
measure the free stroke. If the free stroke is good, but
the applied stroke is too long, there is a problem with
the foundation brake. Check the foundation brake for
missing or worn components, cracked brake drums,
or improper lining to drum contact.
If the free stroke is greater than the recommended
distance (3/8” to 5/8”), a function test of the slack
adjuster should be performed. To test the function
of the slack adjuster, place a 7/16” box wrench
on the hex extension and rotate it 3/4 of a turn
counterclockwise. A ratcheting sound will be heard.
Mark the 7/16” hex extension with chalk and apply
the brakes several times and watch for the hex to
rotate clockwise.
The hex extension must rotate clockwise. The
adjustment is intentionally made in small increments
so it will take several cycles to bring the adjuster
within the stroke limit shown in the chart.
If the free stroke is less than 3/8”, a dragging brake
can occur. Check to see that the manual adjustment
procedure was followed correctly. Manually readjust
the brake following the procedure on page 6-10.
2. Check the torque by attaching a torque wrench to the
hex extension and turning it in a counterclockwise
direction and record the measurement.
3. If the hex extension did not rotate clockwise during
brake application or there is less than 15 ft lbs
of torque required to rotate the hex extension in
the counterclockwise direction, the slack adjuster
must be replaced. If immediate replacement is
not possible, proper brake adjustment must be
maintained by manual adjustment.
4. If the hex extension rotates clockwise and has
a torque of greater than 15 ft lbs when rotated
counterclockwise, the slack is functioning properly.
Check the foundation brake for proper function, worn
cam bushing, pins and rollers, broken springs, worn
quick connect clevis, worn clevis bushings and clevis
pins. Repair as necessary and repeat the function
test.
5. Readjust the brake after the function test.
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