CARRIER AS-GUIDE 1T0443 - 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. 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.
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) RadiatorDuring 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