Toyota Pick-ups/Land Cruiser/4Runner 1970-1988

Automatic Hot Air Intake System (HAI)

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OPERATION



See Figures 1, 2 and 3

Carbureted Models Only

This system allows hot air from the exhaust manifold to be routed to the carburetor in cold weather. Instead of cold air being sucked into the air cleaner all the time, a thermo valve in the air cleaner housing closes when the temperature inside the air cleaner falls below a certain point. When the thermo valve is closed, a diaphragm on the air cleaner neck is activated and it opens the air control valve. This prevents cold outside air from entering the air cleaner, but allows the hotter air from around the exhaust manifold to flow in. Not only does this system improve driveability, but it prevents carburetor icing in extremely cold weather.



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Fig. Fig. 1: Auto hot air intake system component layout and vacuum diagram-2F engine



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Fig. Fig. 2: Auto hot air intake system component layout and vacuum diagram-1984 22R engine



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Fig. Fig. 3: Auto hot air intake system component layout and vacuum diagram-1985-88 22R engine

SERVICE



See Figures 4, 5, 6, 7, 8, 9, 10, 11 and 12

Checking the HAI System
  1. Visually inspect all hoses and connections for cracks, leaks or other damage.
  2.  
  3. Remove the air cleaner top.
  4.  



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Fig. Fig. 4: 20R engine HAI system--later models have a slightly different thermo valve

  1. Cool the thermo valve by blowing compressed air on it.
  2.  
  3. With the engine idling and the thermo valve closed (cool), check to see if the air control valve in the neck of the air cleaner is open and allowing hot air to enter the air cleaner.
  4.  
  5. Install the top of the air cleaner and run the engine until it reaches normal operating temperature.
  6.  
  7. Check that the air control valve is now closed and only cool air is being allowed to enter the air cleaner.
  8.  



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Fig. Fig. 5: Removing the vacuum line from the HAI diaphragm



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Fig. Fig. 6: Removing the mounting bracket from HAI diaphragm



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Fig. Fig. 7: Removing the HAI diaphragm from the air cleaner assembly



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Fig. Fig. 8: Removing the vacuum lines from the air cleaner



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Fig. Fig. 9: Removing the vacuum lines from the engine



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Fig. Fig. 10: Removing the thermo valve vacuum hose



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Fig. Fig. 11: Removing the thermo valve mounting screws



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Fig. Fig. 12: Removing the thermo valve assembly

 
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