A pressure type cooling system gives two advantages. First, the cooling system can be operated safely at a temperature that is higher than the boiling point of water. Also, cavitation in the water pump is reduced. It is more difficult for air or steam pockets to be made in the cooling system.
Note: In an Air-To-Air Aftercooler (ATAAC) system, use a coolant mixture with a 30 percent ethylene glycol base. The ethylene glycol base must be used for efficient water pump performance. This mixture keeps the temperature range of the coolant high enough for efficient performance.
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| Illustration 1 | g00974201 |
Cooling system for a warm engine (1) Cylinder head (2) Water temperature regulators (3) Outlet hose (4) Vent line (5) Vent tube (6) Shunt line (7) Elbow (8) Water pump (9) Cylinder block (10) Coolant diverter valve (11) Precooler (12) Oil cooler (13) Radiator | |
During operation, water pump (8) sends most of the coolant from radiator (13) to oil cooler (12) .
The coolant from oil cooler (12) goes into cylinder block (9) through a bonnet and an elbow. The coolant flows around the cylinder liners into the cylinder head.
Some of the coolant from the elbow is directed toward the precooler (11). If the coolant temperature is below 20 °C (68 °F), the solenoid is energized, and coolant is blocked from the precooler. If the coolant temperature is above 20 °C (68 °F), the coolant diverter valve is open. With the coolant diverter valve open, coolant is allowed to flow through precooler (11) in order to cool the compressed intake air.
The flow of coolant into the head goes around the valves and the passages for exhaust gases in the cylinder head. The coolant then goes to the front of the cylinder head. Then the water temperature regulators (2) control the flow of the coolant into the radiator (13) .
Water temperature regulators (2) are closed when the engine is cold. The coolant flows through the regulator housing and elbow (7) back to water pump (8). This process is done in order to increase the operating temperature of the engine coolant.
If the coolant is at normal operating temperature, water temperature regulators (2) open and the coolant flows to radiator (13) through the outlet hose (3). The coolant becomes cooler as the coolant moves through the radiator. When the coolant gets to the bottom of the radiator, the coolant goes through inlet hose and into water pump (8) .
Note: Water temperature regulators (2) are an important part of the cooling system. Water temperature regulator (2) divides the coolant flow between radiator (13) and bypass elbow (7), maintaining the correct temperature.
Shunt line (6) gives several advantages to the cooling system. The shunt line gives a positive coolant pressure at the water pump inlet that prevents pump cavitation. A small flow of coolant constantly goes through the shunt line (6) to the inlet of water pump (8). This shunt line causes a small amount of coolant to move constantly through vent tube (5). The flow through the vent tube is small and the volume of the upper compartment is large. Air in the coolant is removed as the coolant goes into the upper compartment.
The vent line is used to fill the cooling system with coolant for the first time. This vent line will purge any air out of the top of a bottom filled system.
The OEM may supply a surge tank. The tank can be mounted on the radiator or the tank can be mounted on a remote location. The coolant that expands past the radiator cap is retained in the surge tank. The coolant contracts as the temperature drops and the coolant is drawn back into the radiator.
Coolant For Air Compressor
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| Illustration 2 | g00614143 |
Coolant flow in air compressor (1) Air compressor (2) Outlet hose (3) Inlet hose | |
The coolant for air compressor (1) comes from the cylinder block through inlet hose (3) and into the air compressor. The coolant goes from the air compressor through outlet hose (2) back into the front of the cylinder head.
Coolant Conditioner (An Attachment)
Some conditions of operation can cause pitting on the outer surface of the cylinder liners and on the cylinder block surface next to the cylinder liners. 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 a fuel filter and to oil filter elements. The coolant conditioner element attaches to coolant conditioner base that is mounted on the engine or mounted on a remote location. Coolant flows through lines from the water pump to the base and back to water pump. Coolant constantly flows through the coolant conditioner element.
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. Two basic types of elements are used for the cooling system: the precharge element and the maintenance element. 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 elements should remain in the system after the conditioner has dissolved. This process will allow proper flow of the coolant through the engine. Refer to Operation and Maintenance Manual, "Supplemental Coolant Additive (SCA)" for more information.
The precharge element contains more than the normal amount of the inhibitor. The precharge element is used with new coolant after a complete change of the 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. Refer to Operation and Maintenance Manual, "Maintenance Interval Schedule" for the correct maintenance of the cooling system.