3406E and 3456 Industrial Engines Systems Operation – Cooling System

This engine has a pressure type cooling system that is equipped with a shunt line.

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. Next, cavitation in the water pump is prevented. It is more difficult for air or steam pockets to be made in the cooling system.

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.

Illustration 1 g00290888
Cooling system for a warm engine

(1) Cylinder head. (2) Water temperature regulator. (3) Outlet hose. (4) Vent line. (5) Vent tube. (6) Shunt line. (7) Elbow. (8) Water pump. (9) Cylinder block. (10) Oil cooler. (11) Inlet hose. (12) Radiator.

In operation, the water pump (8) sends most of the coolant from the radiator (12) to the oil cooler (10) .

The coolant from the oil cooler (10) goes into the cylinder block (9) through a bonnet and an elbow. The coolant goes around the cylinder liners, through the water directors and into the cylinder head.

The water directors send the flow of coolant around the valves and the passages for exhaust gases in the cylinder head. The coolant then goes to the front of the cylinder head. At this point, water temperature regulator (2) controls the direction of coolant flow.

The water temperature regulator (2) is closed when the engine is cold. The coolant flows through the regulator housing and elbow (7) back to water pump (8) .

If the coolant is at normal operating temperature, the water temperature regulator (2) opens and the coolant flows to the radiator (12) 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 the inlet hose (11) and into the water pump (8) .

Note: The water temperature regulator (2) is an important part of the cooling system. The water temperature regulator (2) divides the coolant flow between the radiator (12) and the bypass elbow (7). This will maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control. Most of the coolant will go through the bypass. This will cause the engine to overheat in hot weather. If a higher volume of coolant goes through the radiator, the engine will not reach normal operating temperatures. This occurs during cold weather.

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 shunt line (6) to the inlet of water pump (8). This causes a small amount of coolant to move constantly through the 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 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 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

Illustration 2 g00290889
Coolant flow in air compressor

(1) Air compressor. (2) Outlet hose. (3) Inlet hose.

The coolant for the 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)

Illustration 3 g00290890
Schematic of cooling system with coolant conditioner (typical example)

(1) Temperature regulator housing. (2) Coolant outlet to radiator. (3) Vent line with orifice at cylinder head. (4) Radiator. (5) Shunt line. (6) Bypass. (7) Water pump. (8) Coolant conditioner element. (9) Engine oil cooler. (10) Coolant temperature sensor. (11) Coolant inlet from radiator.

Some conditions of operation can cause pitting on the outer surface of the cylinder liners and on the cylinder block surface next to the 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.

Coolant conditioner element (8) 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 the air compressor (accessories). 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. 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 elements should remain in the system so that coolant will flow through after the conditioner material is 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.

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