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 flow of coolant to the water pump.
Raw water is drawn in through the inlet of the auxiliary water pump. The raw water will flow through the fuel cooler before the auxiliary water pump inlet if the engine is equipped with the optional fuel cooler. The raw water is forced out of the pump and into the aftercooler. The raw water flows through the aftercooler and exits at the end of the aftercooler. The raw water then travels through the marine gear cooler(if equipped), the heat exchanger, and the exhaust elbow (if equipped). The raw water is then discharged.
The water pump is located on the side of the cylinder block. The water pump is belt driven from the crankshaft pulley.
Coolant from the heat exchanger is pulled into the bottom inlet of the water pump by impeller rotation. The coolant exits the pump directly into the oil cooler cavity.
The coolant enters the internal water manifold of the cylinder block. The manifold disperses the coolant to water jackets around the cylinder walls.
The coolant from the rear of the cylinder block supplies the exhaust manifold and the turbocharger.
The coolant then flows into passages in the cylinder head. The passages send the flow around the unit injector sleeves and the inlet and the exhaust passages.
The coolant exits the cylinder head and combines with the flow of coolant from the exhaust manifold before entering the regulator. The coolant then flows through a deaerator in order to purge excess air to the expansion tank. Air vents are provided on the water outlet of the turbocharger and at the rear of the cylinder head. The air vents allow the cooling system to fill with coolant. The air vents also remove the air from the cooling system.
Note: The water temperature regulator 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 from the cylinder head to the inlet of the water pump. When the coolant temperature reaches the normal operating temperature, the water temperature regulator opens. Coolant then travels to the heat exchanger for cooling.
Note: The water temperature regulator is an important part of the cooling system. The water temperature regulator divides coolant flow between the heat exchanger and the bypass in order to maintain the normal operating temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will travel the path of least resistance through the bypass. This action will cause the engine to overheat in hot weather and the engine will not reach normal operating temperature in cold weather.
The shunt line extends from the top of the water pump to the expansion tank. The shunt line must be routed properly in order to avoid trapping any air. By providing a constant flow of coolant to the water pump, the shunt line prevents the water pump from cavitating.