ELBOW 4N8581 - Caterpillar

This engine has a pressure type cooling system that is equipped with a shunt line.A pressure type cooling system offers two advantages:
The cooling system can operate safely at a temperature that is higher than the normal boiling point of water.
The cooling system prevents cavitation in the water pump.Cavitation is the sudden formation of low pressure bubbles in liquids by mechanical forces. The formation of air or steam pockets is more difficult within a pressure type cooling system.The shunt line prevents cavitation by the water pump. The shunt line provides a constant head pressure at the water pump inlet.Note: The coolant mixture must be a minimum of 30 percent ethylene glycol base antifreeze for efficient water pump performance for air to air after cooled engines. The mixture keeps the cavitation temperature range of the coolant high enough for efficient performance.
Illustration 1 g01167052
Cooling system schematic (1) Cylinder head (2) Water temperature regulator housing (3) Expansion tank (4) Shunt line (expansion tank to water pump) (5) Bypass hose (6) Radiator (7) Cylinder block (8) Clean Gas Induction (CGI) canister (9) Oil cooler (10) Water pumpWater pump (10) is located on the right side of the cylinder block. The water pump is belt driven from the crankshaft pulley. Coolant can enter the water pump in three places:
Inlet at the bottom of the water pump
Bypass hose (5) into the top of the water pump
Shunt line (4) into the top of the water pumpCoolant from the bottom of the radiator is pulled into the bottom inlet of the pump by impeller rotation. The coolant exits the back of the pump directly into the oil cooler cavity of the block.All of the coolant passes through the core of the oil cooler and the coolant enters the internal water manifold of the cylinder block. The manifold disperses the coolant to water jackets around the cylinder walls.
Illustration 2 g01218677
Water Lines Group (1) Cylinder head (2) Water temperature regulator housing (5) Bypass hose (10) Water pump (11) Outlet to radiator (12) Water temperature regulator (13) Air vent valve in thermostat (14) CGI inlet hoseFrom the cylinder block, the coolant flows into passages in the cylinder head. The coolant flows from the cylinder head into the head of the CGI cooler. The coolant flows from the CGI cooler back to the cylinder head. The passages send the flow around the unit injector sleeves and the inlet and the exhaust passages. The coolant now enters water temperature regulator housing (2) at the front right side of the cylinder head and the CGI canister from an opening at the rear of the head.Water temperature regulator (12) controls the direction of flow. When the coolant temperature is below the normal operating temperature, the water temperature regulator is closed. The coolant is directed through bypass hose (5) and into the top inlet of the water pump. When the coolant temperature reaches the normal operating temperature, water temperature regulator (12) opens. When the water temperature regulator is open, the bypass is closed. Most of the coolant