In the case of a non temperature controlled type that consists of a paper element, turn the wing nut at the upper side of the air filter box cover and the cover should be removed at the set time intervals. Then the filter element has to be thrown away, the interior of the casing has to be cleaned, a new filter element should be put in and the cover has to be put back. In the case of a temperature controlled air filter box using a plain paper element, do as has been explained above. If used, the paper element should be removed after removing the Polywrap band in the Polywrap element. If the band comes out undamaged, wash it in kerosene and pat it dry, and then soak it in clean engine oil, remove excess and fit on a new paper element and rebuild. To perform a diagnostic check for problems of the temperature controlled air filter box, the engine should be started when cold and with the mirror look up the intake nozzle to see the deflector flap being close to cold air and open to warm air. The flap should be open to cold air after the engine has warmed up and should be closed to warm air, both of the tests should be conducted when the vehicle is idle. The vacuum unit can be unbolted by drilling through the two spot welded areas to demount the retaining strip and the new vacuum unit repair pack will contain the screws required for this process. The sensor can only be detached by pulling up the tab of the retaining clip in the tray.