The cooling system consists of the following components (see Figure 20515 ):
1. Oil Cooler Housing
5. Water Bypass Tube
2. Thermostat Housing
6. Water Pump
3. Vent Line Outlet
7. Water Inlet
4. Water Outlet (To Radiator)
Cooling System Components
An OEM supplied radiator along with a factory installed and thermo-modulated fan are used to effectively dissipate the heat generated by the engine. A centrifugal-type water pump is used to circulate the engine coolant.
Two full blocking-type thermostats are used in the water outlet passage to control the flow of coolant, providing fast engine warm-up and regulating coolant temperature. Listed in Table are the normal cooling system operational parameters.
The pressurized engine coolant is drawn from the lower portion of the radiator by the water pump and is forced through the oil cooler and into the cylinder block. See Figure 21519 .
Coolant Flow Schematic for Vehicle and Industrial Engines
On marine engines, coolant from the fresh water pump flows through the engine in three circuits: Coolant flowing into the oil cooler passes through the cylinder block, the cylinder head, and the thermostat housing before moving on to the heat exchanger. See Figure 35404 and see Figure 36037 . Coolant going to the water-cooled exhaust manifold flows directly back to the thermostat housing and then into the heat exchanger, where it is cooled. Coolant going to the water-cooled turbocharger flows into the bypass (rapid warm-up) cooling circuit and back to the pump.
Coolant Flow Schematic for Heat Exchanger-Cooled Marine Engine
Coolant Flow Schematic for Keel-Cooled Marine Engine
On keel-cooled marine engines, fresh water coolant flow is similar to the flow on vehicle engines, except that it passes through a keel cooler instead of a radiator. See Figure 35405 and see Figure 36038 .
Raw Water Flow on Heat Exchanger-Cooled Marine Engine
Raw Water Flow on Keel-Cooled Marine Engine
When the engine is at normal operating temperature, the coolant passes from the cylinder block up through the cylinder head, through the thermostat housing and into the upper portion of the radiator. The coolant then passes through a series of tubes where the coolant temperature is lowered by the airflow created by the revolving fan and the motion of the vehicle.
Upon starting a cold engine or when the coolant is below operating temperature, the closed thermostats direct coolant flow from the thermostat housing through the bypass tube to the water pump. Coolant is recirculated through the engine to aid engine warm-up. When the thermostat opening temperature is reached, coolant flow is divided between the radiator inlet and the bypass tube. When the thermostats are completely open, all of the coolant flow is to the radiator inlet.
The function of the engine coolant is to absorb the heat, developed as a result of the combustion process in the cylinders, from component parts such as the valves and pistons which are surrounded by water jackets. In addition, the heat absorbed by the oil is also removed by the engine coolant in the oil-to-water oil cooler. Coolant recommendations for the Series 60 engine are listed in Table .
A pressurized cooling system permits higher temperature operation than a non-pressurized system. It is essential that the cooling system is kept clean and leak-free, that the filler cap and pressure relief mechanisms are properly installed and operate correctly, and that the coolant level is properly maintained.
As the engine temperature increases, the coolant and air in the system starts to expand and build pressure. The valve in the radiator pressure cap unseats and allows the coolant to flow into the coolant recovery tank. See Figure 20457 .
When the engine starts to cool down, the air and coolant contract, causing a void and creating a vacuum in the system. The vacuum unseats another valve in the pressure cap, allowing the coolant to flow back into the expansion tank, radiator or heat exchanger tank. See Figure 20458 .