SHAFT-PLANETARY 2V4148 - Caterpillar

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