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