Section 4.1
Overview of Cooling System
The cooling system consists of the following components (see Figure "Cooling System Operation" ):
- Water Pump
- Pressure Control Cap
- Thermostat
- Engine Coolant Fan
- Coolant and Coolant Conditioner
- Radiator
1.Weep Hose
3.Thermostat Housing and Thermostat
2.Water Pulley and Water Pump
4.Water Manifold
Figure 1. Cooling System Operation
An OEM supplied radiator along with a factory installed 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.
One full blocking-type thermostat is used in the water manifold to control the flow of coolant, providing fast engine warm-up and regulating coolant temperature.
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 "Typical Coolant Flow Schematic" .
Figure 2. Typical Coolant Flow Schematic
When the engine is at normal operating temperature, the coolant passes from the cylinder block up through the water manifold and into the upper portion of the radiator. The coolant then passes through the radiator where the coolant temperature is lowered by the air flow 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 directed 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 air-to-oil cooler.
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.
| Series 638 Service Manual - 6SE648 |
| Generated on 10-13-2008 |