DAF CF65, CF75, CF85 Series . Manual - part 908

©

 200423

2-17

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

2.11 INSPECTION, PARKING BRAKE VALVE

Parking brake valve with trailer control and 
test position

1.

Ensure there is sufficient system pressure.

2.

Connect pressure gauges to connection 
point (43) of the trailer control valve and to 
connection point (12) of a spring brake 
cylinder.

Inspecting the driving position
1.

Place the parking brake valve in the driving 
position. Both pressure gauges must now 
indicate a pressure of approx. 8.5 bar. 
This is the limiting pressure of the pressure 
limiting valve.

Inspecting the emergency brake
1.

Move the parking brake valve slowly 
towards the parking position. Both pressure 
gauges should now gradually fall to 0 bar 
(with the exception of the first 10

 angular 

displacement. See graph in 
"Technical data").

Inspecting the parking position
1.

In the parking position, both pressure 
gauges should read 0 bar.

Inspecting the test position
1.

Place the parking brake valve in the parking 
position, depress the handle, and move it to 
the test position. The pressure gauge at 
connection point (43) of the trailer vehicle 
control valve should read approx. 8.5 bar. 
The pressure gauge on the connection 
point of the spring brake cylinder should read 
0 bar.

3

21

1

22

a

2
3

5

4

6

8

7

9

10

R600092

BRAKE SYSTEM AND COMPONENTS

2-18

©

 200423

Inspection and adjustment

5

ΧΦ65/75/85 series

6

Parking brake valve without trailer control
1.

Ensure there is sufficient system pressure.

2.

Connect a pressure gauge to 
connection (12) of a spring brake cylinder.

Inspecting the driving position
1.

Place the parking brake valve in the driving 
position. The pressure gauge must now 
indicate a pressure of approx. 8.5 bar 
(see graph in "Technical data").

Inspecting the emergency brake
1.

Move the parking brake valve slowly 
towards the parking position. The pressure 
gauge should now gradually fall to 0 bar 
(with the exception of the first 10

 angular 

displacement. See graph in "Technical 
data").

Inspecting the parking position
1.

In the parking position, the pressure gauge 
should read 0 bar.

R600095

2

7

3

4

5

6

1

3

2

a

©

 200423

2-19

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

2.12 CHECK AND ADJUST INPUT AND OUTPUT PRESSURES OF THE AIR 

SUPPLY UNIT

Inspecting the cut-out pressure
1.

Connect a pressure gauge to the central 
drain/filler connection.

2.

Pressurise the air system.

3.

Check that the pressure regulator cuts out at 
the correct reading.

4.

If this is not the case, adjust the value using 
the screw on the air dryer (see arrow) as 
follows:

Adjusting the cut-out pressure
1.

If the cut-out pressure is too low, tighten the 
adjusting screw a little so that the cut-out 
pressure becomes too high.

2.

Ensure that the pressure regulator is 
switched on. If it is switched off, let some air 
escape through a reservoir until the system 
pressure falls beneath the cut-in pressure.

3.

Pressurise the air system to a little over 
10 bar.

4.

Unscrew the adjusting screw until the 
pressure regulator cuts out (see "Technical 
data").

5.

Check the cut-out pressure in the way 
mentioned above (see "Technical data").

Adjusting trailer vehicle system pressure
1.

Fit a pressure gauge to the trailer supply 
connection (red connection).

2.

Build up pressure in the brake system 
(air dryer should blow off).

3.

Check the pressure (see "Technical data").

4.

If necessary, adjust the pressure by turning 
the adjusting screw.

R600480

R600652

BRAKE SYSTEM AND COMPONENTS

2-20

©

 200423

Inspection and adjustment

5

ΧΦ65/75/85 series

6

2.13 CHECK AIR DRYER REGENERATION FUNCTION IN THE AIR SUPPLY UNIT

Air dryer regeneration function
1.

Pressurise the air system 
(pressure regulator should cut out).

2.

Switch the engine off.

3.

The regeneration air should escape 
via the vent opening of the air dryer, 
for approximately 20 seconds.

2.14 CHECK THE 4-CIRCUIT SECURITY VALVE OF THE AIR SUPPLY UNIT

Check pressure build-up on circuits 1, 2, 3 and 4
1.

Lower the pressure in the system to 0 bar.

2.

Connect pressure gauges to circuits 1, 2, 
3 and 4.

3.

Pressurise the circuits using the compressor 
(engine speed approx. 1000 rpm).

4.

The pressure in circuits 1, 2 and 4 will 
gradually increase. Once the opening 
pressure of circuit 3 has been reached 
(see "Technical Data"), the pressure in 
circuit 3 will increase.

5.

If no more pressure builds up (cut-out 
pressure reached), the supply pressure in 
circuits 1, 2, 3 and 4 must meet the stipulated 
value (see "Technical Data").

Checking circuit 1
1.

Turn off the engine and simulate a leak in 
circuit 1.

2.

The pressure in circuit 2 and 4 may not fall 
below the specified closing pressure of 
circuit 1. See "Technical data".

Checking circuit 2
1.

Make sure the leak in circuit 1 is remedied 
and pressurise the system again.

2.

Turn off the engine and simulate a leak in 
circuit 2.

3.

The pressure in circuit 1 and 4 may not fall 
below the specified closing pressure of 
circuit 2. See "Technical data".