COOLANT FLOW FOR RADIATOR COOLING SYSTEM (Jacket Water Aftercooled – JWAC)
1. Radiator. 2. Pressure cap. 3. Inlet line for radiator. 4. Exhaust manifold. 5. Turbocharger. 6. Aftercooler. 7. Return line from aftercooler. 8. Aftercooler inlet line. 9. Internal bypass (shunt) line. 10. Water pump. 11. Inlet line for water pump. 12. Engine oil cooler. 13. Auxiliary oil cooler. 14. Bonnet.
Water pump (10) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of radiator (1) goes to the water pump inlet. The rotation of the impeller in water pump (10) pushes the coolant through the system.
The coolant flow from water pump (10) is divided. Some goes through engine oil cooler (12). Bonnet (14) on the outlet side of engine oil cooler (12) connects to the side of the cylinder block.
On engines with an auxiliary oil cooler (13) a different bonnet (14) is on engine oil cooler (12). This bonnet (14) sends the coolant flow through auxiliary cooler (13) which is for attachments such as torque converters or marine gears. The flow goes through one side on the way into auxiliary oil cooler (13). At the bottom of auxiliary oil cooler (13) the flow turns and goes back up through the other side and into bonnet (14) again. Then bonnet (14) sends the coolant into the cylinder block.
The remainder of the coolant flow goes through aftercooler inlet line (8) into the core of aftercooler (6). The core of aftercooler (6) is a group of plates and fins. The coolant goes through the plates. The inlet air for the engine goes around the fins. This cools the inlet air. The coolant comes out of the aftercooler (6) at the rear of the engine and goes through return line (7) to bonnet (14) on engine oil cooler (12). It mixes with the rest of the coolant from engine oil cooler (12) in bonnet (14) and goes into the cylinder block.
Inside the cylinder block, the coolant goes around the cylinder liners and up through the water directors 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 goes to the front of the cylinder head. Here the water temperature regulator controls the direction of the flow. If the coolant temperature is less than normal for engine operation, the water temperature regulator is closed. The only way for the coolant to get out of the cylinder head is through internal bypass (shunt) line (9). The coolant from this line goes into water pump (10) which pushes it through the cooling system again. The coolant from internal bypass (shunt) line (9) also works to prevent cavitation (air bubbles) in the coolant. When the coolant gets to the correct temperature, the water temperature regulator opens and coolant flow is divided. Some goes through radiator (1) for cooling. The rest goes through internal bypass (shunt) line (9) to water pump (10). The proportion of the two flows is controlled by the water temperature regulator.
NOTE: The water temperature regulator is an important part of the cooling system. It divides the coolant flow between radiator (1) and internal bypass (9), as necessary, to maintain the correct operating temperature. If the regulator is not installed, there is no mechanical control, and most of the coolant will take the path of least resistance thru internal bypass line (9). This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes thru radiator (1) is too much, and the engine will not get up to normal operating temperature.
Internal bypass (shunt) line (9) has another function when the cooling system is being filled. It lets the coolant go into the cylinder head and cylinder block without going through water pump (10).
Radiator (1) has a pressure cap (2). This cap controls pressure in the cooling system.