COVER 6F9168 - Caterpillar

Coolant Flow
COOLANT FLOW
1. Radiator. 2. Inlet line to radiator. 3. Water temperature regulator. 4. Cylinder head. 5. Cylinder block. 6. Inlet line to water pump. 7. Water pump. 8. Internal bypass. 9. Engine oil cooler. 10. Elbow.Water pump (7) is on the left front of the engine. The water pump is gear driven by the front timing gears. The rotation of the impeller in the water pump pushes coolant through the cooling system.Coolant from the bottom of radiator (1) is pulled through inlet line (6) by water pump (7). The water pump pushes coolant to engine oil cooler (9). Coolant flows from the engine oil cooler through elbow (10) into the side of cylinder block (5) and flows around the cylinder liners and up through the coolant directors into cylinder head (4). The coolant directors make the coolant flow around the valves and around the exhaust ports (passages) in the cylinder head. The coolant now goes to the front of the cylinder head. At the front of the cylinder head water temperature regulator (3) controls the direction of the coolant flow. If the coolant temperature is less than normal for engine operation, the water temperature regulator is closed. The coolant must go through internal bypass (8) to the water pump. When the coolant gets to the temperature of normal operation the water temperature regulator opens and most of the coolant flows through radiator inlet line (2) to the radiator. A part of the coolant still goes through internal bypass (8). The water temperature regulator (3) is an important part of the cooling system. It divides coolant flow between radiator (1) and internal bypass (8) as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.