DAF CF65, CF75, CF85 Series . Manual — part 907

©

200423

2-13

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

2.8 INSPECTING THE RELAY VALVE

Inspecting the relay valve
1.

Connect a pressure gauge to connecting
point (4) of the relay valve.

2.

Connect a pressure gauge to connecting
point (2) of the relay valve.

3.

Pressurise the system.

4.

Depending on the position of the relay valve
in the brake system, slowly activate the
service brake or parking brake.

5.

The pressure in the pressure gauge
connected to connection point (4) must now
increase to approx. 0.8 bar (the increased
parking brake actuating pressure) or 0.5 bar
(service brake), without there being any
noticeable pressure on connection point (2).
From this point, the pressures in both
pressure gauges must increase identically.
The pressure on the gauge connected
to point (2) should not rise in jumps.
Both gauges should indicate a value
corresponding to the graph. See "Technical
data".

R600490

2

1

6

4

A

5

3

7

BRAKE SYSTEM AND COMPONENTS

2-14

©

200423

Inspection and adjustment

5

ΧΦ65/75/85 series

6

2.9 INSPECTION, TRAILER VEHICLE CONTROL VALVE

1.

Ensure there is sufficient system pressure.

2.

Check whether air is escaping via the bleed
vent.

3.

Depress the brake pedal, and again check
for leaks.

4.

Disconnect the pipe at connecting point (42)
and plug off this pipe.

5.

Depress the brake pedal, and check
for pressure build-up in the service pipe
(see "Technical data").

6.

Reconnect the pipe.

7.

Repeat the last three points, but now for
connecting point (41).

8.

Operate the parking brake: pressure should
build up in the service pipe (see "Technical
data").

9.

Operate the parking brake to the stop,
and lock the lever: the service pipe should
once again become pressureless.

10. Simulate a leak in the service pipe,

and depress the brake pedal; within
two seconds, the outflow of air from the leak
should slow down considerably.

R600340

©

200423

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Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

2.10 INSPECTION AND ADJUSTMENT, ADVANCE IN TRAILER VEHICLE

CONTROL VALVE

Inspection, braking pressure advance in
trailer vehicle control valve

Note:
The pressure ratio between prime mover and
drawn vehicle is 10 : 8 (10 bar system pressure
for prime mover and 8 bar system pressure for
drawn vehicle).

This means that if no braking pressure advance
is applied, at an input pressure of 3 bar at
connection point (41), the output pressure at
connection point (2) is equal to (3 x 8): 10 = 2.4
bar.

If a braking pressure advance of 0.6 bar is now
applied, the output pressure at connection point
(2) should be 2.4 + 0.6 = 3.0 bar.

1.

Connect a pressure gauge (1) to the test
connection for the load sensing valve and
a pressure gauge (2) to the service coupling
head.

2.

Depress the brake pedal until the input
pressure (measured at pressure gauge 1)
is 3 bar. The reading at pressure gauge (2)
should now be 3.0 bar. This equals 0.6 bar
braking pressure advance.

3.

If the braking performance of the trailer
vehicle (provided it is in good condition)
is poorer than that of the prime mover,
the advance may be increased by several
tenths of a bar.

BRAKE SYSTEM AND COMPONENTS

2-16

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200423

Inspection and adjustment

5

ΧΦ65/75/85 series

6

Adjusting the advance in trailer vehicle
control valve

Note:
The pressure at which the readings are taken
must always be built up. If the specified pressure
is exceeded, bleed off sufficient air, and once
again allow the pressure to build up.

1.

Remove the plug.

Note:
Make sure that the valve is not operated
when the advance is adjusted.

2.

Using a 6mm Allen key, turn the central
section (7) anti-clockwise or clockwise
to decrease or increase the advance
respectively.

3.

Measure the advance again.

4.

Repeat these actions until the required
advance is reached.

5.

Re-fit the plug.

41

42

3 bar

6 mm

43

11

12

+

_

22

R600341