G3500B Engines Cooling System Caterpillar


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

The engine has two cooling systems. The jacket water system cools the following components: engine oil cooler, cylinder block, cylinder heads, turbochargers and aftercooler's first stage. A separate system cools the aftercooler's second stage. Illustrations 1 and 2 are diagrams of typical cooling systems.



Illustration 1g00811028
The cooling system has two pumps that are driven by the engine. Coolant from the jacket water cools the first stage of the aftercooler. The separate circuit cools the second stage.


Illustration 2g00811012
Cooling system for the jacket water and a separate circuit for the two-stage aftercooler that operates at a standard temperature

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

Jacket Water System

The jacket water pump is located 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 the radiator or the heat exchanger enters the water pump's inlet. 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 to the front of the cylinder block and into the main distribution manifold for the water jacket of each cylinder. The remainder of the coolant flows through the engine oil cooler.

After flowing through the engine oil cooler, this portion of the coolant is divided again. Some of the coolant flows into the water jacket of the right rear cylinder. This coolant is mixed throughout the engine's water jacket with the coolant that flows to the front of the cylinder block. The remainder of the coolant flows through the first stage of the aftercooler.

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 and the coolant flows into the water manifold.

Coolant flows through the water manifold into lines for the turbocharger turbine housing and for the exhaust bypass valve. The coolant returns to the water manifold.

Air is vented from the high points of the cooling system. 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 water manifold directs the coolant to the water temperature regulator housing. The engine has eight water temperature regulators. The water 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 the radiator or through the heat exchanger. This coolant circulates back to the jacket water pump. The remainder of the coolant goes through a bypass tube 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 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



Illustration 3g00998688
Typical example
(1) Auxiliary water pump
(2) Tube for the coolant supply to the aftercooler's second stage
(3) Aftercooler
(4) Tube for the coolant return from the aftercooler to the thermostatic valve
(5) Thermostatic valve
(6) Outlet for coolant to the radiator or heat exchanger
(7) Inlet for coolant from the radiator or heat exchanger

Auxiliary water pump (1) is driven by the engine's auxiliary drive. The coolant is pumped through tube (2) to the aftercooler's second stage (3). The coolant exits the aftercooler through tube (4) that is connected to thermostatic valve (5).

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 flows to a radiator or to a heat exchanger through outlet (6). The coolant returns to the auxiliary pump through inlet (7).

Information System:

953C Track-Type Loader Hydraulic System Lift Cylinder
Cat Digital Voltage Regulator General Information
963C Track-Type Loader Coolant Sample (Level 1) - Obtain - Diesel Engine Antifreeze/Coolant (DEAC)
950G and 962G Wheel Loaders and IT62G Integrated Toolcarrier Power Train Transmission Planetary - Disassemble
963C Track-Type Loader Capacities (Refill)
963C Track-Type Loader Engine Starting
TH220B, TH330B and TH340B Telehandlers Hydraulic System General Information Table
988G Wheel Loader Cooling System Coolant Sample (Level 1) - Obtain
Cat Monitoring System Numeric Readout Mode
953C Track-Type Loader Hydraulic System Hydraulic Tank and Filter
615C Series II Wheel Tractor-Scraper Wheel Tractor Power Train Axle Shaft - Remove
953C Track-Type Loader Power Train Electronic Control Module Manifold
D6N Track-Type Tractor Power Train Steering Clutch and Brake - Disassemble
D6N Track-Type Tractor Power Train Steering Clutch and Brake - Assemble
950G and 962G Wheel Loaders and IT62G Integrated Toolcarrier Power Train Transmission Planetary - Assemble
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E283 Low Hydraulic Charge Pressure
980H Wheel Loader Service Brake Control
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E623 Low Left Track Forward Steering Pressure
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E624 Low Left Track Reverse Steering Pressure
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E625 Low Right Track Forward Steering Pressure
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E626 Low Right Track Reverse Steering Pressure
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E702 High Left Track Steering Pressure
953C, 963C and 973C Track-Type Loaders Transmission Electronic Control System E703 High Right Track Steering Pressure
980G Series II Wheel Loader Operation Information