Description
1. The air filter is thermally controlled, the air is heated to a temperature that is most suitable for combustion with a minimum level of exhaust gas emissions.
2. Optimum air temperature is achieved by mixing cold air from the inlet duct on the front of the vehicle with hot air heated in a shroud on the exhaust manifold. The proportion of hot and cold air is controlled by the position of the flap in the flow of the air filter inlet, which is controlled by either a vacuum diaphragm or a wax block. The vacuum diaphragm is controlled by a temperature sensor located in the air filter housing (see illustration).
Examination
3. To test the operation of the air temperature control, the engine must initially be cold. First check the position of the flap. On the vacuum regulator, remove the air filter cover and make sure the flap is open, letting in only cold air from outside the car. Then start the engine and check that the flap has now moved, letting only hot air out of the exhaust manifold.
On a wax regulator, the flap should be positioned so that only hot air from the exhaust manifold passes through.
4. Temporarily install the cover on the vacuum regulator.
5. Start the engine and warm up to normal operating temperature.
6. On the vacuum regulator, remove the air filter cover and make sure the flap is now positioned so that only cold air from outside the car passes through. In cold weather, hot and cold air must mix. On the wax regulator, use a mirror to check that the flap is positioned in the same way as on the vacuum regulator.
7. If the flap does not function correctly, the air filter housing must be replaced. Please note that the vacuum thermostat can be replaced separately.
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