G3500H Generator Set Engine Cooling System Caterpillar


Cooling System
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1.1. Jacket Water System
2.1. Separate Circuit System

The engine has two cooling systems. The jacket water system cools the following components: engine oil cooler, cylinder block, cylinder heads, turbochargers, and aftercooler first stage. A separate system cools the aftercooler second stage.

Water temperature regulators are used in each circuit to maintain correct operating temperatures.



Illustration 1g06278572
G3512H cooling system

Jacket Water System



Illustration 2g06278197
G3512H cooling system
(1) Inlet for the jacket water pump
(2) Jacket water pump
(3) Bypass tube
(4) Tube for the coolant supply to the aftercooler (first stage)
(5) Tube for the coolant supply to the front of the cylinder block
(6) Oil cooler
(7) Tube for the coolant supply to the back right side of the cylinder block
(8) Tube from the cylinder head
(9) Lower water temperature regulator housing
(10) Coolant manifolds
(11) Water temperature regulator housing
(12) Outlet for coolant to radiator or heat exchanger
(13) Aftercooler (first stage)


Illustration 3g06278865
(10) Coolant manifold
(13) Aftercooler (first stage)
(14) Coolant supply from cylinder block to turbocharger
(15) Turbocharger
(16) Coolant return from turbocharger to manifold
(17) Vent location

The jacket water pump (2) is on the right front side of the engine. The water pump has a gear that is driven by the lower right front gear group. Coolant from a radiator or a heat exchanger enters the water pump inlet (1). The rotation of the impeller in the jacket water pump pushes the coolant through the system.

The flow of the coolant is divided. Some of the coolant from the jacket water pump flows through a tube (4) to the first stage of the aftercooler (13). The coolant leaves the aftercooler and supplies the front of the cylinder block (5). The remainder of the coolant flows through the engine oil cooler (6). The coolant leaves the oil cooler and supplies the back of the cylinder block (7). This coolant is mixed throughout the water jacket with the coolant that flows to the front of the cylinder block.

The coolant inside the cylinder block flows around the cylinder liners. The water jacket is smaller near the top of the cylinder liners. This shelf causes the coolant to flow faster for better cooling of the cylinder liner. The coolant is pumped up through water directors into the cylinder heads. The coolant flows through passages around these items in the cylinder head: valves, valve seat inserts, spark plug adapter and exhaust outlets.

The coolant exits the cylinder heads through tubes (8) into the coolant manifolds (10). Coolant flows through the line (14) to the turbocharger turbine housing (15). The coolant returns to the coolant manifold (10).

Air is vented from the high points of the cooling system (17). The vent line from the connection must be straight and the vent line must have a slight upward slope. The vent must not be obstructed.

The coolant manifold directs the coolant to the water temperature regulator housing (11). The temperature regulator housing contains multiple temperature regulators. The temperature regulators control the direction of the coolant flow according to the coolant temperature.

When the coolant achieves normal operating temperature, the water temperature regulators open and coolant flow is divided. Most of the coolant goes through a radiator or through a heat exchanger. This coolant circulates back to the jacket water pump (2). The remainder of the coolant goes through a bypass tube (3) to the jacket water pump.

Note: The water temperature regulators are necessary to maintain the correct engine temperature. If the water temperature regulators are not installed in the system, there is no mechanical control. Most of the coolant will take the path of least resistance through the bypass tube. This condition will cause the engine to overheat in hot weather. The small amount of coolant that goes through the radiator in cold weather will not allow the engine to achieve normal operating temperatures. The water temperature regulators control the minimum temperature of the coolant. The radiator or the heat exchanger controls the maximum temperature of the coolant.

The bypass tube has another function. When you fill the cooling system the internal bypass allows the coolant to go into the cylinder head and into the cylinder block without going through the water pump.

The total system capacity depends on the amount of coolant in the cylinder block, in the piping, and in the radiator or heat exchanger.

Separate Circuit System



Illustration 4g06492466
(1) Auxiliary water pump
(2) Tube for the coolant supply to the aftercooler second stage
(3) Tube for the coolant return from the aftercooler to the thermostatic valve
(4) Aftercooler (second stage)
(5) Inlet for coolant from the radiator or heat exchanger
(6) Outlet for coolant to radiator or heat exchanger

Auxiliary water pump (1) is driven by the engine auxiliary drive. The coolant is pumped through tube (2) to the aftercooler second stage (4). The coolant exits the aftercooler through tube (3) that is connected to the thermostatic valve.

The thermostatic valve has one inlet, two outlets, and a water temperature regulator. When the coolant is cool, the water temperature regulator is closed. The coolant is routed directly back to the auxiliary water pump. The coolant is recirculated through the aftercooler.

When the coolant reaches the opening temperature, the water temperature regulator opens. The coolant is routed to a radiator or to a heat exchanger through outlet (6). The coolant returns to the auxiliary pump through inlet (5).

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