See Figures 1 and 2
The heated air intake portion of the air cleaner consists of a thermostat or bimetal switch along with a vacuum motor and a spring loaded temperature control door in the snorkel of the air cleaner. The temperature control door is located between the end of the air cleaner snorkel which draws in air from the engine compartment and the duct that carries heated air up from the exhaust manifold. When underhood temperature is below 90°F (32°C), the temperature control door blocks off underhood air from entering the air cleaner and allows only heated air from the exhaust manifold to be drawn into the air cleaner. When underhood temperature rises above 130°F (54°C), the temperature control door blocks off heated air from the exhaust manifold and allows underhood air to be drawn into the air cleaner.
By controlling the temperature of the engine intake air this way, exhaust emissions are lowered and fuel economy is improved. In addition, throttle plate icing is reduced, and cold weather driveability is improved from the necessary leaner mixtures.
Duct and Valve Assembly
- Either start with a cold engine or remove the air cleaner from the engine for at least half an hour. While cooling the air cleaner, leave the engine compartment hood open.
- Tape a thermometer, of known accuracy, to the inside of the air cleaner so that it is near the temperature sensor unit. Install the air cleaner on the engine but do not fasten its securing nut.
- Start the engine. With the engine cold and the outside temperature less than 90°F (32°C), the door should be in the HEAT ON position (closed to outside air).
- Operate the throttle lever rapidly to 1 / 2 - 3 / 4 of its opening and release it. The air door should open to allow outside air to enter and then close again.
- Allow the engine to warm-up to normal temperature. Watch the door. when it opens to the outside air, remove the cover from the air cleaner. the temperature should be over 90°F (32°C) and no more than 130°F (54°C). Keep in mind that 105°F (41°C) is about normal. If the door noes not work within these temperature ranges, or fails to work at all, check for linkage or door binding.
If binding is not present and the air door is not working, proceed with the vacuum tests given below. If these indicate no faults in the vacuum motor and the door is not working, the temperature sensor is defective and must be replaced.Vacuum Motor
Be sure that the vacuum hose that runs between the temperature switch and the vacuum motor is not pinched by the retaining clip under the air cleaner. This could prevent the air door from closing.
- Check all vacuum lines and fittings for leaks. Correct any leaks. If none are found, proceed with the test.
- Remove the hose which runs from the sensor to the vacuum motor. Run a hose directly from the manifold vacuum source to the vacuum motor.
- If the motor closes the air door, it is functioning properly and the temperature sensor is defective.
- If the motor does not close the door and no binding is present in its operation, the vacuum motor is defective and must be replaced.
If an alternate vacuum source is applied to the motor, insert a vacuum gauge in the line by using a T-fitting. Apply at least 9 in. Hg (30 kPa) of vacuum in order to operate the motor.
REMOVAL & INSTALLATION
Duct and Valve Assembly
- Remove the hex-head cap screws which secure the air intake duct and valve assembly to the air cleaner.
- Remove the air intake duct and valve assembly from the engine.
- If the duct and valve assembly was removed because of a suspected temperature malfunction, check the operation of the thermostat and valve plate assembly. Refer to the Duct and Valve Assembly test for the proper procedure.
If inspection reveals that the valve plate is sticking or the thermostat is malfunctioning, remove the thermostat and valve plates as follows:
- Detach the valve plate tension spring from the plate using long-nosed pliers.
- Loosen the thermostat locknut and unscrew the thermostat from the mounting bracket.
- Grasp the valve plate and withdraw it from the duct.
- Install the air intake duct and valve assembly on the shroud tube.
- Connect the air intake duct and valve assembly to the air cleaner and tighten the hexhead retaining cap screws.
If it was necessary to disassemble the thermostat, air duct and valve, assemble the unit as follows:
- Install the valve plate. Install the locknut on the thermostat, and screw the thermostat into the mounting bracket. Install the valve plate tension spring on the valve plate and duct.
- Check the operation of the thermostat and air duct assembly. Refer to the Duct and Valve Assembly test for the proper procedure. Tighten the locknut.
- Install the vacuum override motor (if applicable) and check for proper operation.
- Disconnect the vacuum hose at the vacuum motor.
- Remove the hex head cap screws which secure the air intake duct and valve assembly to the air cleaner.
- Remove the duct and valve assembly from the engine.
- Position the duct and valve assembly to the air cleaner and heat stove tube. Install the attaching cap screws.
- Connect the vacuum line at the vacuum motor.