DAF LF45, LF55 Series. Manual — part 439
©
200436
1-1
Disc brake construction
DIAGNOSTICS
ΛΦ45/55 series
6
1
1. DISC BRAKE CONSTRUCTION
1.1 FAULT-FINDING TABLE
SYMPTOM: SQUEALING/NOISE DURING BRAKING
Possible cause
Remedy
Worn brake pads
Check brake pads and brake disc thickness
Loose parts
Check disc brake construction
Wear/damage to hub bearing
Check hub bearing play
Wear to internal parts of disc brake construction
Check internal parts
Incorrect vehicle combination
Check vehicle combination
Incorrect front axle / rear axle brake pressure
balance
Check front axle / rear axle balance
SYMPTOM: IRREGULAR BRAKE PAD WEAR
Possible cause
Remedy
Fouled/corroded guide bushes
Check the guide bushes
Dirt accumulation between moving parts of the disc
brake construction
Clean the disc brake construction
Moisture and dirt on internal mechanical parts
Check and clean the brake calliper seals
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
SYMPTOM: VEHICLE PULLS TO ONE SIDE DURING BRAKING
Possible cause
Remedy
Difference in tyre pressure
Check / correct tyre pressure
Difference in tyre size
Check tyres
Different brake cylinder diameters
Check brake cylinder diameters
Broken springs in brake cylinders
Check brake cylinders
Leaking brake cylinders
Check brake cylinders
Fouled brake cylinders
Check the brake cylinders for fouling
Excessive stub axle bearing play
Check stub axle bearing play
Excessive steering ball joint play
Check steering ball joint play
Excessive shackle pin play
Check shackle pin play
Incorrect vehicle combination
Check vehicle combination
Incorrect ABS operation
Check ABS operation
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
DIAGNOSTICS
1-2
©
200436
Disc brake construction
1
ΛΦ45/55 series
6
SYMPTOM: POOR BRAKING DECELERATION
Possible cause
Remedy
Overload due to excessive loading
Check vehicle loading condition
System pressure too low
Check pressure regulator setting
Air leakage in the brake system
Check the brake system for leakage
Insufficient braking power / poor condition of trailer
vehicle brake system
Check trailer vehicle
Pinched brake lines
Check / replace brake lines
Brake cylinder stroke too large
Check automatic slack adjuster
Frozen brake system
Check brake system
Brake components affected by road salt
Check the brake components for fouling.
Fouled brake cylinders
Check the brake cylinders for fouling
Incorrect brake cylinder diameter
Check brake cylinders
Incorrect operation / setting of load sensing valve
Check operation / setting of load sensing valve
Incorrect vehicle combination
Check vehicle combination
Incorrect ABS operation
Check ABS operation
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
SYMPTOM: VIBRATIONS DURING BRAKING
Possible cause
Remedy
Incorrect wheel tightening procedure
Tighten wheels according to tightening procedure
Non-standard wheels fitted
Fit only standard wheels
Overload due to excessive loading
Check vehicle loading condition
Incorrect front axle / rear axle brake pressure
balance
Check front axle / rear axle balance
Wrong brake pad quality
Check brake pads
Dirt/deposits on brake disc
Check/clean brake disc
Loose parts
Check disc brake construction
Wear/damage to hub bearing
Check hub bearing play
Damage to disc brake
Check thickness and condition of brake disc
Play in cab suspension
Check cab suspension
Incorrect vehicle combination
Check vehicle combination
©
200436
1-3
Disc brake construction
DIAGNOSTICS
ΛΦ45/55 series
6
1
SYMPTOM: LOCKING OF THE BRAKES
Possible cause
Remedy
Incorrect setting of load sensing valve
Check setting of load sensing valve
Thermal overload of non-locking axle brake pads
Check non-locking axle brake pads
Incorrect system pressure due to incorrect
pressure regulator setting
Check pressure regulator setting
Defective trailer vehicle brake system
Check trailer vehicle brake system
Incorrect vehicle combination
Check vehicle combination
Incorrect ABS operation
Check ABS operation
Tyres have too little tread
Check tread
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
SYMPTOM: INCREASED BRAKE PAD WEAR
Possible cause
Remedy
Overload due to excessive loading
Check vehicle loading condition
Incorrect setting of load sensing valve
Check setting of load sensing valve
Incorrect vehicle combination or front axle/rear
axle balance
Check vehicle combination or front axle/rear axle
balance
Defective trailer vehicle brake system
Check trailer vehicle brake system
Air pressure in spring brake cylinders too low
during driving, dragging brakes
Check air pressure in spring brake cylinders with
the parking brake valve in the driving position
Dragging brakes because parking brake is not
released
Check release of parking brake
Dirt under foot brake valve / floor mat too high
Check for free movement of foot brake valve
Dirty / blocked brake valve bleeders
Check valve bleeders
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
Incorrect setting of the trailer vehicle control valve/
trailer vehicle reaction valve
Check setting of the trailer vehicle control valve/
trailer vehicle reaction valve
DIAGNOSTICS
1-4
©
200436
Disc brake construction
1
ΛΦ45/55 series
6
SYMPTOM: DRAGGING BRAKES
Possible cause
Remedy
Leaking foot brake valve to circuit 1 and/or 2
Check the foot brake valve for leaks
Dirt/deposits in brake calliper of disc brake
Check freedom of movement of brake calliper
Brake pads turned back too tightly
Check minimum brake pad play
Air pressure in spring brake cylinders too low
during driving
Check output pressure of the double-check relay
valve
Check four-circuit safety valve for dirt
Check output pressure of the parking brake valve
in the driving position
Output supply pressure from trailer vehicle control
valve to trailer/semi-trailer too low
Check output supply pressure of the trailer vehicle
control valve
Dirt under foot brake valve / floor mat too high
Check for free movement of foot brake valve
Dirty / blocked brake valve bleeders
Check valve bleeders
Brake pad stuck in the brake calliper Incorrect play
between brake pads and brake carrier
Check the play between brake pads and brake
carrier
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