DAF LF45, LF55 Series. Manual - part 456

©

 200436

2-3

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΛΦ45/55 series

6

4

2.3 INSPECTION AND ADJUSTMENT, LOAD SENSING VALVE, AIR 

SUSPENSION

Explanatory notes on instruction plate
The information contained on the plate relates to 

the axle loads, the output pressures and bellows 

pressures, in accordance with the order of axles 

beneath the vehicle.

"1" refers to the (first) front axle, "2" to the 

following axle, etc.

In the entire column, a reading of 6 bar has been 

filled in under "1".

If the vehicle is equipped with an empty/load 

valve, a pressure ratio is entered in the box under 

the valve illustration, e.g. "i = 1 : 1.5". The 

"delivery pressure p2" of axle "1" then indicates 

variable readings.

These values can be used to check the brake 

pressure values of the front axle and to carry out 

the inspection/adjustment below at the same 

time. To do this, connect a pressure gauge to the 

test connection of one of the front axle brake 

cylinders.

Inspection/adjustment
1.

Check that the correct valve has been fitted 

(see instruction plate).

2.

Connect pressure gauge 4 to the test 

connection close to connecting point 1/4 on 

the load-dependent control valve (input 

pressure).

3.

Connect pressure gauge 2 to the test 

connection on one of the brake cylinders 

(service brake connection) of the rear axle.

4.

Connect a pressure gauge (43) with a 

pressure-reducing valve to the simulation 

connection near connections 41 and 42 of 

the load-sensing valve (= simulated 

adjustable bellows pressure).

5.

Make sure that the reservoir pressure is 

higher than 6.5 bar throughout the testing 

process.

6.

Set the simulated bellows pressure to its 

second lowest value, as indicated on the 

instruction plate.

7.

Depress the brake pedal until pressure 

gauge 4 indicates a pressure of 6 bar.

R6 00 548

43

1/4

4

2

2

R600473

1

41 42

r

s

BRAKE SYSTEM AND COMPONENTS

2-4

©

 200436

Inspection and adjustment

4

ΛΦ45/55 series

6

8.

Read the brake pressure of the rear axle on 

pressure gauge 2 and check that this brake 

pressure matches the one listed on the 

instruction plate in the table under "output 

pressure p2" to the rear axle.

9.

If the measured value is not correct, 

depressurise connection 43 and, using a 

special slotted-nut spanner, special tool 

(DAF no. 1329464), turn the adjusting nut(s):

-

brake pressure too high: unscrew the 

adjusting nut

-

brake pressure too low: screw in the 

adjusting nut

Note:

When depressurising the simulation 

connection (pressure gauge 43), the air hose 

must remain connected to prevent the 

(actual) bellows pressure from accidentally 

activating the valve.

The small socket head screw in the centre of 

the valve must not be adjusted.

10. Repeat the procedure described in point 6 

until the measured brake pressure value is 

within the tolerance limits.

11. Set the simulated bellows pressure to its 

second highest value, as indicated on the 

instruction plate.

12. Depress the brake pedal until pressure 

gauge (4) indicates a pressure of 6 bar.

13. Read the pressure gauge (2) and check that 

this braking pressure matches the pressure 

indicated in the table on the instruction plate.

14. If the measured reading is not correct, 

depressurise connection 43 and turn the 

adjusting bolt (r) using a Torx screwdriver:

-

brake pressure too high: screw in the 

adjusting bolt

-

brake pressure too low: unscrew the 

adjusting bolt

Note:

When depressurising the simulation 

connection (pressure gauge 43), the air hose 

must remain connected to prevent the 

(actual) bellows pressure from accidentally 

activating the valve.

The small socket head screw in the centre of 

the valve must not be adjusted.

15. If the adjusting bolt (r) has been turned, 

repeat the procedure from point 6.

R600478

43

1/4

4

2

2

R600473

1

41 42

r

s

©

 200436

2-5

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΛΦ45/55 series

6

4

2.4 INSPECTION AND ADJUSTMENT, LOAD SENSING VALVE, 

LEAF SUSPENSION

Explanatory notes on instruction plate
The data relating to axle loads and output 

pressures are listed on the instruction plate 

following the sequence of the axles beneath the 

vehicle.

"1" refers to the (first) front axle, "2" to the 

following axle, etc.

In the entire column, a reading of 6 bar has been 

filled in under "1". If the vehicle is equipped with 

an empty/load valve, a pressure ratio is entered 

in the box under the valve illustration, e.g. 

"i = 1 : 1.5". The "output pressure P2" of axle 1 will 

give variable readings.

These values can be used to check the brake 

pressure values of the front axle and to carry out 

the inspection/adjustment below at the same 

time. To do this, connect a pressure gauge to the 

test connection of one of the front axle brake 

cylinders.

Inspection/adjustment
1.

Measure the weight plus load of the rear 

axle.

2.

Check the attachment of the control lever 

and its ease of operation.

3.

Check that the right type of valve has been 

fitted.

4.

Check the length of the control lever (see "L" 

on the instruction plate).

5.

Connect a pressure gauge (4) to the test 

connection near connection 1/4 on the load-

sensing valve (input pressure).

6.

Connect a pressure gauge (2) to the test 

connection on one of the brake cylinders 

(service brake connection) of the rear axle.

7.

Make sure that the reservoir pressure is 

higher than 6.5 bar throughout the testing 

process.

8.

Depress the brake pedal until pressure 

gauge 4 indicates a value of 6 bar.

9.

Read the brake pressure of the rear axle 

from pressure gauge 2 and check that this 

value matches the one listed on the 

instruction plate in the table under "output 

pressure p2" to the rear axle.

R6 00 549

1/4

4

2

2

R600562

1

BRAKE SYSTEM AND COMPONENTS

2-6

©

 200436

Inspection and adjustment

4

ΛΦ45/55 series

6

10. If necessary, correct the brake pressure by 

adjusting the length of the vertical 

connecting rod (2). Never attempt to alter 

length L of the (horizontal) control lever.

11. Remove the ball coupling (1) and raise the 

control lever. Check that the output pressure 

is now allowed through (almost) without 

reduction.

Note:

The small socket head screw in the centre of 

the valve must not be adjusted.

1

2

R6 00 568

L