This type of system prevents cavitation in the water pump. Cavitation is the forming of low pressure bubbles in liquids that are caused by mechanical forces. The formation of an air pocket or a steam pocket in this type of cooling system is difficult.
The shunt line prevents cavitation by the water pump. The shunt line provides a constant flow of coolant to the water pump.
Note: In air to air aftercooled systems, a coolant mixture with a minimum of 30 percent ethylene glycol base antifreeze must be used for efficient water pump performance. This mixture keeps the cavitation temperature range of the coolant high enough for efficient performance.
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| Illustration 1 | g00837373 |
Cooling system schematic (1) Cylinder head (2) Water temperature regulator housing (3) Bypass hose (4) Cylinder block (5) Oil cooler (6) Water pump (7) Radiator (8) Expansion tank (9) Shunt line (expansion tank to water pump) | |
Water pump (6) is located on the right front side of cylinder block (4). The water pump is belt driven from the crankshaft pulley. Coolant can enter the water pump in three places:
- the inlet at the bottom of the water pump
- the bypass hose (3) into the top of the water pump
- the shunt line (9) into the top of the water pump
Coolant from the bottom of radiator (7) is pulled into the bottom inlet of the water pump by the impeller rotation. The rotation of the impeller in the water pump forces the coolant through the cooling system. The coolant exits the back of the water pump directly into the oil cooler cavity of the cylinder block.
All of the coolant passes through the core of oil cooler (5) and the coolant then enters the internal water manifold of cylinder block (4). This manifold distributes the coolant to water jackets that are around the cylinder walls.
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| Illustration 2 | g00837374 |
Water lines group (1) Cylinder head (2) Water temperature regulator housing (3) Bypass hose (6) Water pump (10) Outlet to radiator (11) Water temperature regulator that is partially open (12) Air vent valve that is located in the flange of thermostat (13) Coolant return from the air compressor (if equipped) (14) Port for water pump outlet pressure for engine diagnosis | |
Note: Later thermostats have an air vent valve (12). This air vent valve allows air to escape from the cooling system while coolant is added.
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| Illustration 3 | g00837375 |
Water lines group (2) Water temperature regulator housing (3) Bypass hose (6) Water pump (10) Outlet to radiator (11) Water temperature regulator that is partially open | |
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| Illustration 4 | g00837376 |
Water pump (15) Pump outlet pressure (alternate heater supply) (16) Port for coolant supply to aftercooler (if equipped) (17) Coolant return ports from the heater (18) Alternate pump outlet pressure for engine diagnosis | |
From the cylinder block, the coolant flows into passages that are in cylinder head (1). These passages send the flow of coolant around the following items:
- Unit injector sleeves
- Inlet passages
- Exhaust passages
The coolant now enters water temperature regulator housing (2) at the front right side of cylinder block (4) .
Water temperature regulator (11) controls the direction of flow. If the temperature of the coolant is below normal, then the water temperature regulator is closed. The coolant is directed through bypass hose (3) and into the top inlet of water pump (6). When the coolant gets to the correct temperature, the water temperature regulator will open. Most of the coolant goes through outlet (10) to the radiator for cooling. The remainder flows through the bypass hose and into the water pump.
The shunt line (9) extends from the top of the water pump to an 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 keeps the water pump from cavitation.
Note: Water temperature regulator (11) is an important part of the cooling system. The water temperature regulator divides the coolant flow between the radiator and the bypass in order to maintain the proper temperature. If the water temperature regulator is not installed in the system, then there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. Any amount of coolant that flows through the radiator can be too much in cold weather. This will cause the engine not to reach normal operating temperatures.
Coolant For Air Compressor (If Equipped)
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| Illustration 5 | g00835748 |
Coolant lines for air compressor (6) Water pump (19) Coolant supply line (20) Coolant return line (21) Air compressor | |
If the engine is equipped with an air compressor, coolant is supplied to air compressor (21) through coolant supply line (19). The coolant is circulated through air compressor (21). The coolant is returned to the cooling system through coolant return line (20) .
Coolant Conditioner (If Equipped)
Some conditions of operation can cause pitting. This pitting is caused by corrosion or by cavitation erosion. A corrosion inhibitor is a chemical that provides a reduction in pitting. The addition of a corrosion inhibitor can keep this type of damage to a minimum.
The coolant conditioner element is a spin-on element that is similar to the fuel filter and to the oil filter elements. The coolant conditioner element attaches to the coolant conditioner base that is mounted on the front of the engine. Coolant flows from the water pump to the coolant conditioner base and back to the cylinder block. Coolant constantly flows through the coolant conditioner element when the valves are in the OPEN position.
The element has a specific amount of inhibitor for acceptable cooling system protection. As the coolant flows through the element, the corrosion inhibitor goes into the solution. The corrosion inhibitor is a dry solution, so the inhibitor dissolves. The corrosion inhibitor then mixes to the correct concentration. Two basic types of elements are used for the cooling system. The two elements are the precharge elements and the maintenance elements. Each type of element has a specific use. The elements must be used correctly in order to get the necessary concentration for cooling system protection. The elements also contain a filter. After the conditioner material is dissolved, the elements should remain in the system so that coolant will flow through the system.
The precharge element contains more than the normal amount of inhibitor. The precharge element is used when a system is first filled with new coolant. This element must add enough inhibitor in order to bring the complete cooling system up to the correct concentration.
The maintenance elements have a normal amount of inhibitor. The maintenance elements are installed at the first change interval. A sufficient amount of inhibitor is provided by the maintenance elements in order to maintain the corrosion protection at an acceptable level. After the first change interval, only maintenance elements are installed. In order to provide the cooling system with protection, maintenance elements are installed at specific intervals.