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 head pressure at the water pump inlet.
Note: The coolant mixture must be a minimum of 30 percent ethylene glycol base antifreeze for efficient water pump performance for air to air after cooled engines. The mixture keeps the cavitation temperature range of the coolant high enough for efficient performance.
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| Illustration 1 | g01155880 |
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(1) Cylinder head
(2) Water temperature regulator housing (3) Expansion tank (4) Bypass hose (5) Radiator (6) Cylinder block (7) Engine oil cooler (8) Transmission oil cooler (if equipped) (9) Water pump | |
Water pump (9) is located on the right side of the cylinder block. The water pump is gear-driven from the front gear group. Coolant can enter the water pump in two places:
- Inlet at the bottom of the water pump
- Bypass hose (4) at the top of the water pump
Coolant from the bottom of the radiator (5) is pulled into the bottom inlet of the water pump (9) by impeller rotation. The coolant exits the back of the pump directly into engine oil cooler (7). Some of the coolant is also diverted to transmission oil cooler (8) (if equipped).
Some of the coolant passes through the core of engine oil cooler (7) and some of the coolant passes through the core of transmission oil cooler (8) (if equipped). The coolant then enters the internal water manifold of the cylinder block. The manifold disperses the coolant to water jackets around the cylinder walls.
From the cylinder block, the coolant flows into passages in the cylinder heads. The passages send the flow around the unit injector sleeves and the inlet and the exhaust passages. The coolant now enters water temperature regulator housing (2) at the front of the cylinder head.
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| Illustration 2 | g01155995 |
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(2) Water temperature regulator housing
(4) Bypass hose (9) Water pump (10) Outlet to the radiator (11) Inlet from the radiator | |
Two water temperature regulators control the direction of coolant flow. When the coolant temperature is below the normal operating temperature, the water temperature regulators are closed. The coolant is directed through bypass hose (4) and into the top inlet of the water pump. When the coolant temperature reaches the normal operating temperature, the water temperature regulators open. When the water temperature regulators are open, the bypass is closed. Most of the coolant goes through the outlet to the radiator for cooling. The remainder flows through bypass hose (4) and into the water pump.
Note: The water temperature regulators are an important part of the cooling system. The water temperature regulators divide coolant flow between the radiator and the bypass hose in order to maintain the normal operating temperature. If the water temperature regulators are 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 hose. This will cause the engine to overheat in hot weather and the engine will not reach normal operating temperature in cold weather.
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. The coolant conditioner elements should remain in the system after the conditioner material has dissolved.
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.