Thermostatic Air Cleaner: Testing and Inspection

NOTE:
An improperly operating heated air inlet system can affect driveability and the vehicle's exhaust emission.


DIAGNOSIS/SERVICE

Perform the following procedure to determine if the air inlet system is functioning properly.

PROCEDURE

Heated Inlet Air System Vacuum Hose Routing:

1. Be sure that the heat stove-to-air cleaner flexible connector, air cleaner duct and all vacuum hoses are properly attached. Be sure that they are in good condition.

2. With a cold engine and ambient temperature less than 44°C (112°F.), heat control door in snorkel should be in the up (heat on) position.

3. With the engine warmed up and running, check the air temperature entering the snorkel or at the sensor. When air temperature entering outer end of snorkel is 54.4°C (130°F) or higher, door should be in the down (heat off) position.

4. Remove the air cleaner from the engine and allow it to cool down to 44.4°C (112°F). With 20 inches of vacuum applied to the sensor, the door should be in the up or (heat on position). If the door does not rise to the heat on position, check the vacuum diaphragm for proper operation.

Testing Heated Air Inlet Vacuum Diaphragm:

5. To test the diaphragm, apply 25 inches of vacuum with vacuum pump Tool C-4207 or equivalent. The diaphragm should not bleed down more than 10 inches of vacuum in 5 minutes. The door should not lift off bottom of snorkel when less than 2.5 inches of vacuum is applied to diaphragm. The door should be in full up position with no more than 4.0 inches vacuum applied to diaphragm.

6. If the vacuum diaphragm does not perform correctly, replace the vacuum diaphragm. Repeat steps 2 and 3.

7. If the vacuum diaphragm performs correctly but proper temperature is not maintained, replace the sensor. Repeat the temperature checks in steps 2 and 3.