The thermostatic air cleaner is a temperature-regulated device which improves engine warm up characteristics and helps to minimize carburetor icing. The air cleaner assembly is equipped with a vacuum operated air control door at the inlet and a bi-metal air bleed valve inside the air cleaner. When the air control door is open, fresh air is heated by flowing over the exhaust manifold, then taken up a hose and into the air cleaner.
The air bleed valve is closed when the air cleaner temperature is less than 77°F (25°C), allowing manifold vacuum to open the air control door and admit heated air to the carburetors. If there is vacuum to the intake air control door above that temperature, the air bleed valve is faulty and should be replaced.
Apply vacuum to the air control door diaphragm. If the diaphragm does not hold vacuum, it must be replaced. Also, make certain the hot air tube is connected to the bottom of the intake duct and to the exhaust manifold shield at the other end. Quite often, the hose gets overlooked when the air cleaner is removed. This could cause cold driveability problems.
CONTROL DOOR DIAPHFRAGM REPLACEMENT
See Figures 1 and 2
To remove the air control door diaphragm, simply disconnect the vacuum hose, then twist and remove the diaphragm from the air cleaner.