BENDIX BW7514 User Manual
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All foundation brakes are designed to convert kinetic energy (energy of motion) into heat
and work (to stop the vehicle).
Air disc brakes work the same way and in everyday operation — compared to drum brakes
— will produce higher braking temperatures and cool off faster. Also, air disc brakes
will often have differences in temperatures at wheel ends on the same axle. The actual
temperatures reached will depend on the vehicle conguration, vocation and brake usage.
This document is intended to help technicians identify instances where an individual wheel
end has evidence of thermal overload, and check for potential causes.
SECTION ONE: Inspect the Vehicle
Question One:
Do any of the rotors have
bright orange or red
color edges?
Check the box(es) on the
vehicle diagram to the
right for any found.
Normal Evidence of thermal overload
Question Two:
Are any of the calipers
coated with a bright
orange or red colored
dust? Check the box(es)
on the vehicle diagram to
the right for any found.
Normal Evidence of thermal overload
Bendix® Air Disc Brake
Checklist for
Identifying Single Wheel
End Thermal Overload
Follow all General Safety
Guidelines (see nal page.)
c L. Steer
c L. Drive c R. Drive
c L. Add’l.
Steer Axle
Drive
Axle
Additional
Axle
c R. Steer
c R. Add’l.
Check
box(es)
where
Thermal
Overload is
suspected.
Question Three:
Are any tappets and/or
guide pin boots heat
damaged? Check the
box(es) on the vehicle
diagram to the right
for any found.
Typical Evidence of thermal
overload
Are
any boxes
checked?
YES
Are
both boxes
on a single axle
checked?
NO
Only
one box has a
check mark?
NO
Evidence of thermal
overload
YES
YES
Trailer Front
c L. Trlr. Front
c L. Trlr. Rear
Axle
Trailer Rear
Axle
c R. Trlr. Front
c R. Trlr. Rear
STOP!
Exit this
owchart.
This is not a single wheel end
Thermal Overload event.
When both ends of an axle are
affected, a thorough brake system
diagnosis is needed, as other
factors — such as brake balance,
overloaded vehicles, or extreme
use — are more likely the source.
Go to Section Two (over)
NO
In cases where more than one wheel end is affected — but on different
axles — complete a separate checklist for each brake being examined.
SECTION TWO: Investigate Other Potential External Causes
• Follow all Safe Maintenance Practices (see nal page.)
Inspect the brake pads.
(New pads have 21 mm of brake pad, plus a 9 mm backing plate.)
Is
there
2 mm, or less, of
YES
brake pad friction
material?*
NO
Replace the pads (axle set recommended)
after performing all Section Two inspections.
(Not a Thermal Overload warranty condition.)
*2 mm of friction material, plus a 9 mm
backing plate, for a total of 11 mm.
Inspect the
caliper
Inspect the
air hoses
(“jounce
lines”).
Push/pull
by hand to check the
caliper movement
[at least 0.75 Inch
(20 mm) with the
pads removed]
Does
the brake
caliper have
restricted movement in
YES
the inboard/outboard
direction?
NO
• Is air trapped in the hose?**
• Do the hose(s) pull or push on the caliper? (It is
important that the hoses permit the lateral motion of
the caliper, the vertical motion of the suspension, and
— for steering axles — the full turn of the wheels.)
• Are there any kinks, restrictions?
• Are the hoses in good condition?
Complete this
step on level
ground, with the
wheels chocked
and the parking
brake temporarily
released!
Service the guide pins.
Perform all Section Two inspections.
(Not a Thermal Overload warranty condition.)
**Take full safety precautions during the inspection
for trapped air, to avoid the air hose whipping if air
pressure is found to be trapped. Conditions that
might cause trapped air include kinked lines, or
when an ABS modulator is malfunctioning and
not exhausting service air.
Are
any of
these conditions
found?
NO
Go to the next page . . .
YES
Service as needed.
Perform all Section Two inspections.
(Not a Thermal Overload warranty condition.)
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