Air cleaner temperature control check (24 000 Mile (40 000 Km) / every 2 years)
Note: A vacuum pump will be required for this check if the heat sensor or diaphragm unit is at fault.
1 The air cleaner temperature control unit can be checked for operation whilst the engine is cold. Look into the air inlet spout and check that the air control flap valve is in the shut position.
Air cleaner inlet sensor and diaphragm flap valve operating modes
1 Sensor cold 2 Sensor hot
2 Now start the engine and allow it to idle. The flap valve should open fully to allow the warm air to be drawn into the cleaner unit from the exhaust manifold ducting. As the engine warms up to its normal operating temperature the flap valve should progressively close to allow cooler air to enter the cleaner unit.
3 If the valve is stuck in the shut position, check the vacuum lines for condition and security. If these are in order, then the heat sensor or diaphragm unit is at fault. Proceed as follows:
4 Detach the diaphragm-to-heat sensor vacuum pipe (at the sensor end) and connect up a vacuum pump to the diaphragm. Pump and apply a vacuum up to 100 mm of mercury and retain this whilst checking the air flap.
5 If the flap opens, the heat sensor is defective and must be renewed, but if it remains shut then the diaphragm or control flap is faulty.
6 Disconnect the vacuum pump and reconnect the vacuum pipe to the sensor unit.