Bleeding Air from the Cooling System

Jiggle pin thermostats are original equipment on units that have engines from the TK486 family of engines. Jiggle pin thermostats make it unnecessary to bleed the air out of the engine block because they keep air from being trapped in the engine block. Normally, all but about 1.5 qt (1.4 liters) of coolant drain out of the cooling system when it is drained. If approximately half of the Cooling System Capacity (see Specifications Chapter) seems to fill the cooling system after it has been drained, air has been trapped in the block. Bleed the air out of the block using the following procedure:

1. Remove the plug from the front end of the water pump below the thermostat housing as shown (Remove Plug from Water Pump).

2. Slowly pour the coolant into the system until you see coolant at the plug fitting.

3. Reinstall the plug.

4. Pour coolant into the system until it appears to be full.

   
   

   Remove Plug from Water Pump

   Open

   1.

   Plug

5. Verify that the amount of coolant that goes back into the system is approximately equal to the amount of coolant that came out of the system.

6. Start the engine and monitor the coolant temperature with the unit engine coolant temperature gauge, or by using a non-contact thermometer pointed at the thermostat housing in the location of the high water temperature switch or sensor.

   1. When the temperature reaches 150 F (66 C), shut the engine off for two minutes.

      Note This allows time for the thermostat to heat soak and open fully, ensuring that any remaining air will be purged out of the engine block when the engine is restarted.

7. Restart the engine and run it in low speed.

   1. Remove the cap from the expansion tank and slowly pour coolant into expansion tank until it is full, then reinstall the expansion tank cap.

8. Repeat steps 6 and 7 until the coolant level stabilizes.