CLAS B.LINE AC 0550BL Mode D'emploi page 20

HU 0014BL
METAL TRANSFER PUMP
10 Testing of automatic transmission vacuum modulator valves
Automatic transmissions are normally equipped with a vacuum-actuated modulating valve so
that the automatic transmission can sense engine loads and adjust shift points accordingly.
The AC 0550BL Vacuum Tester can be used to check that the modulator valve diaphragm is
serviceable and also to simulate variable engine loads so that modulator pressure readings
can be recorded.
To test the diaphragm of the modulation valve, remove the vacuum supply line from the
valve and attach the AC 0550BL vacuum tester. Operate the vacuum pump until you reach
approximately 15 inHg and then monitor the pressure gauge reading for approximately 30
seconds. No vacuum drop should be noted. To verify modulator pressure readings, connect a
pressure gauge to the appropriate port on the transmission. Remove the vacuum supply line
from the modulator and connect the product vacuum tester (fi g.13). Start and run the engine
and apply the vacuum pressures. Monitor the readings and confi rm that they are within the
manufacturer's specifi cations. During normal operation, a manifold vacuum reading should be
observed.
11. Braking systems
Brake servo diaphragm test
Remove the vacuum supply line from the brake servo connection. Attach the vacuum tester
of the AC 0550BL to the vacuum supply port of the brake servo (fi g. 14). Operate the pump
to create a vacuum of approximately 15 inHg and wait 30 seconds. No vacuum drop should be
observed on the pressure gauge reading. If the vacuum drops, it indicates that the brake servo
diaphragm is defective. In this case, the servo should be removed for service by an authorized
repairer or replaced.
Brake bleeding - Fitting the brake bleeding kit
Ensure that the vacuum pump is connected to the brake bleed tank in accordance with the
installation diagram (fi g. 15). If this is not the case, the brake fl uid will be sucked into the
vacuum pump.