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7.4.
TESTING VACUUM OPERATED HEATER TAPS
7.4.1.
Climate control ventilation systems are becoming very common on newer vehicles and most of the systems use vacuum operated taps
to control the heating modes. On the majority of makes and models, the system uses vacuum to turn the heater tap 'on'.
7.4.2.
To test these remove the supply line from the tap vacuum module and connect the VS4021 vacuum tester (fig.10). With the engine at
normal operating temperature locate and feel the heater return hose. With the heater tap in the 'off' position, this hose should be cold.
Now operate the vacuum pump to open the tap. The gauge reading must hold. If the tap is in working order, the return hose will begin
to heat. If the hose does not begin to heat, this indicates that the tap is faulty.
7.5.
TESTING VACUUM OPERATED REMOTE CENTRAL LOCKING SYSTEMS
7.5.1.
Some makes and models use vacuum operated bellows mounted in each door to centrally lock and unlock the vehicles doors. These
systems use either manifold vacuum stored in a reservoir for use when the engine is not running or an electrically driven vacuum
pump which operates when the doors are locked or unlocked.
7.5.2.
In either system, the VS4021 vacuum tester is ideal for testing each individual door bellows. To do this, remove the door trims as
required. Remove the vacuum supply lines from the bellows and attach the VS4021 vacuum tester (fig.11) and operate to apply vacuum
to the bellows. Wait for 30 seconds, no drop on the gauge should be noted. If the bellows are found to be in order attach the vacuum
supply line to the VS4021 vacuum tester and operate system to test for vacuum supply. If the vacuum supply does not exist or is low
trace back down the lines to the vacuum supply looking for kinks, restrictions or cracked lines. Repair as required and retest.
7.6.
TESTING AUTOMATIC TRANSMISSION VACUUM OPERATED MODULATOR VALVES
7.6.1.
Automatic transmissions are normally equipped with a vacuum operated modulator valve in order for the automatic transmission to
detect engine loads and adjust shift points to suit.
7.6.2.
The VS4021 vacuum tester can be used to test both that the modulation valve diaphragm is serviceable and also to simulate varying
engine loads so modulator pressure readings can be recorded. To test the modulator valve diaphragm remove the vacuum supply line
from the valve and attach the VS4021 vacuum tester. Operate the vacuum pump until approximately 15 inHg is achieved and monitor
the gauge reading for approximately 30 seconds. No vacuum drop should be noted.
7.6.3.
To check modulator pressure readings attach a pressure gauge to the appropriate port on the transmission. Remove the vacuum
supply line from the modulator and attach the VS4021 vacuum tester (fig.12). Start and run the engine and apply vacuum pressures.
Monitor readings and confirm that these are in conformance with manufacturer specifications.
fig.12
8. BRAKING SYSTEMS
8.1.
TESTING BRAKE SERVO DIAPHRAGM
8.1.1.
Remove vacuum supply line from brake servo fitting. Attach
VS4021 vacuum tester to vacuum supply port on servo (fig.13).
Operate pump to create approximately 15 inHg of vacuum and
wait for 30 seconds. No vacuum drop should be observed on the
gauge reading. If the vacuum drops this indicates that the brake
servo diaphragm is faulty. In this case the servo should be
removed for overhaul by an authorised repairer or replaced.
8.2.
BRAKE BLEEDING - ASSEMBLY OF BRAKE BLEEDER KIT
8.2.1.
Ensure that the vacuum pump is connected to the brake bleeder
reservoir in accordance with the assembly diagram (fig.14). Failure
to do so will result in brake fluid being drawn into the vacuum pump.
© Jack Sealey Limited
fig.10
fig.11
Original Language Version
fig.13
fig.14
VS4021.V2 | Issue 2 (F,2,3) 26/02/19
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