Meritor MM-2075 Maintenance Manual page 28

9 Troubleshooting
Condition Possible Causes
Brake Drag Brake caliper seized/drag
a. Both calipers on
the same axle
Incorrect master cylinder push rod
b. All calipers - all
length
wheel ends
Incorrect brake booster push rod
length
Primary or secondary piston in master
cylinder not returning
Brake pedal binding.
Reservoir cap not venting
Brake drag - drive Park brake not releasing
axle brakes
Lining wear Brake not releasing
difference in the
same caliper -
inboard pad vs
outboard pad
Rotor finish
Contaminates on inboard or outboard
brake pad or brake surface
Operating environment
MM-2075 / Revised 09-23
Page 24
Check for
Refer to above Brake Drag - One
wheel end
Check master cylinder push rod length Adjust per OEM instruction.
Check brake booster push rod length
Check if primary or secondary piston
chamber of master cylinder is holding
pressure
Verify brake pedal fully releases
Pressure build up in brake fluid
reservoir. Remove reservoir cap - any
air press release when cap is removed
indicated cap is not venting and can
cause brake drag
Check park brake and verify releasing
Verify caliper not holding pressure.
Open bleed screw and check if brake
releases.
Inspect piston boots for damage and
contaminate ingress that may be
affecting piston movement
Inspect crossover tube for damage
that could restricted fluid flow
Verify the brake pads move freely
when the pad retainer spring is
removed
Verify the piston is not over extended -
brake pad worn beyond service life
Inspect inboard and outboard braking
surfaces for cracks, heat checking or
wear grooves
Check braking surfaces for
contaminate - grease, oil, brake fluid
Inspect parts for difference in
environmental exposure
Copyright Meritor, Inc., 2023
Correction
Refer to above Brake Drag - One
wheel end.
Adjust per OEM instruction.
Master cylinder piston seized - replace
master cylinder.
Adjust pedal set-up.
Remove obstructions affecting release.
Replace reservoir cap.
Service per OEM instruction.
Hydraulic system issue - refer to
vehicle manufacturer instruction.
Replace caliper or service damage
hardware.
Replace crossover tube.
Clean or replace abutment plates as
needed.
Service piston or replace caliper.
Replace rotor.
Clean and replace parts as needed.
Replace brake pads that have been
contaminated.
Replace brake pads as an axle set.
Review vehicle cleaning schedule
frequency and metrics to address
wheel end debris conditions.
(16579)
Printed in USA