CYLINDER HEAD AS 7W9391 - Caterpillar

"Improved" cooling system. Radiator Fill (A).Optional Smooth ID Fill Neck (B).Petcock "Fill" Vent (C).3/8inch Vent Line (D).Vent/Sensor Tee (E).Optional Petcock Vent (F).Thermostat (G).Heater Return (H). Shunt Line (J). Cooling System Filling Procedure
The engines are in the rear of these busses. In these applications, take special care to insure that the engine cooling system and the bus heater systems are properly filled. Incorrect filling can leave air trapped in the system. This could cause a loss of engine water pump flow which could result in engine overheating. Use the following procedure to fill the engine cooling and bus heater systems.
1. Open all gate valves.2. Open the drain cock on top of the engine.3. Open the valve on the front heater using the heater controls.4. Remove the radiator cap.5. With the engine NOT running, turn the heater booster pump ON.6. Monitor the outlet of the drain cock (see See Step 2).7. Add coolant as required.8. When all the air is purged (indicated by a steady stream of coolant flowing from the drain cock), close the drain cock.9. If just the heater circuit is being filled, the total volume of coolant added should be 7.6 to 9.5 L (2 to 2.5 gal). If both the engine and heater systems are being filled, the total volume of coolant added should be 17.1 L (4.5 gal).10. Start the engine and add coolant as required.11. Install the radiator cap.