Section 4.1 Overview of Cooling System
Overview of Cooling System
The cooling system consists of the following components:
- Water Pump
An OEM supplied radiator is used to dissipate the heat generated by the engine. A water pump is used to circulate the engine coolant. Twin full blocking-type thermostats are used in the water outlet passage to control coolant flow, providing fast engine warm-up and regulating coolant temperature. Pressurized engine coolant is drawn from the radiator and forced through the oil cooler into the cylinder block.
When the engine is at normal operating temperature, coolant passes from the cylinder block, through the cylinder head, through the thermostat housing, and into the upper portion of the radiator.
Whenever a cold engine is started, or the coolant is below normal operating temperature, the closed thermostats direct coolant 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 fully open, all coolant is directed to the radiator inlet. See Figure
"Coolant Flow Schematic"
Figure 1. Coolant Flow Schematic
Engine coolant absorbs the heat resulting from the combustion process and from components surrounded by water jackets. As it circulates through the oil cooler, coolant also absorbs heat from engine oil. For coolant recommendations, refer to "5.3 Coolant"
For the cooling system to operate properly, it must be kept clean and leak-free, the filler cap and pressure relief mechanisms must operate correctly, and the coolant level must be maintained at the proper level.
As the engine temperature increases, the coolant and air in the system expand and build pressure. The valve in the radiator pressure cap opens, and coolant flows into the coolant recovery tank. See Figure
Figure 2. Coolant Expansion
When the engine begins to cool, coolant and air contract, creating a vacuum in the cooling system. The vacuum opens another valve in the radiator pressure cap, and coolant flows into the expansion tank or radiator. See Figure
Figure 3. Coolant Recovery