3304 & 3306 – Heat Exchanger Cooling System (Engines Without Aftercooler)

1. Heat exchanger. 2. Expansion tank. 3. Pressure cap. 4. Vent line. 5. Inlet line. 6. Water cooled manifold or water cooled shield for manifold. 7. Outlet line. 8. Outlet line. 9. Block. 10. Return line. 11. Water cooled shield for turbocharger. 12. Cylinder head. 13. Cylinder block. 14. Bonnet. 15. Oil cooler for torque converter or marine gear. 16. Sea water outlet. 17. Supply line to water pump. 18. Supply line. 19. Water pump. 20. Internal bypass (shunt) line. 21. Sea water inlet. 22. Sea water pump. 23. Engine oil cooler.

Water pump (19) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of expansion tank (2) goes to the water pump inlet. The rotation of the impeller in water pump (19) pushes the coolant through the system.

All of the coolant flow from water pump (19) in the standard system, goes through engine oil cooler (23). Bonnet (14) on the outlet side of engine oil cooler (23) connects to the side of cylinder block (13).

On engines with an additional oil cooler (15), a different bonnet (14) is on engine oil cooler (23). This bonnet (14) sends the coolant flow through the other oil cooler which is for attachments such as torque converters or marine gears. The flow goes through one side on the way into the cooler. At the bottom of the cooler the flow turns and goes back up through the other side and into bonnet (14) again. Bonnet (14) sends the coolant into cylinder block (13).

An engine can have a water cooled manifold or a water cooled shield for manifold (6). If it has either one of these it can also have a water cooled shield for turbocharger (11). The coolant flow from the water pump is divided. Some of the coolant goes through the standard system and some goes into the water cooled manifold or water cooled shield for manifold (6) at the front of the engine. It comes out at the rear of the engine and goes through return line (10) to bonnet (14) on engine oil cooler (23). It mixes with the rest of the coolant from the standard system in bonnet (14) and goes into cylinder block (13).

If the engine has a water cooled shield for turbocharger (11), the supply of coolant for it comes from the bottom of the rear end of the water cooled manifold or water cooled shield for manifold (6). The coolant goes through the water cooled shield for turbocharger (11). It goes out through outlet line (8) to block (9) at the top of the water cooled manifold or water cooled shield for manifold (6). In block (9) it mixes with the rest of the coolant on the way to bonnet (14).

Inside cylinder block (13) the coolant goes around the cylinder liners and up through the water directors into cylinder head (12). The water directors send the flow of coolant around the valves and the passages for exhaust gases in cylinder head (12). The coolant goes to the front of cylinder head (12). 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 cylinder head (12) is through internal bypass (shunt) line (20). The coolant from this line goes into water pump (19) which pushes it through the cooling system again. The coolant from internal bypass (shunt) line (20) 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 expansion tank (2) and around heat exchanger (1), for cooling. The rest goes through internal bypass (shunt) line (20) to water pump (19). 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 heat exchanger (1) and internal bypass (20), 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 (20). This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes thru heat exchanger (1) is too much, and the engine will not get up to normal operating temperature.

Internal bypass (shunt) line (20) has another function when the cooling system is being filled. It lets the coolant go into cylinder head (12) and cylinder block (13) without going through water pump (19).

The coolant flow from the engine goes through outlet line (7) to expansion tank (2) and heat exchanger (1). Heat exchanger (1) is cooled by sea water sent by sea water pump (22) through supply line (18). The sea water cools the engine coolant in expansion tank (2) and goes out through sea water outlet (16).

Expansion tank (2) is the reservoir for the cooling system. It is the highest place in the cooling system. It is the place where the volume of the coolant can change because of heating or cooling without causing too much or too little coolant for the cooling system. Expansion tank (2) has a pressure cap (3) to control the pressure in the cooling system for better operation.

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