PISTON 9J9805 - Caterpillar

Jacket Water Aftercooling
Illustration 1 g03676565
(1) Radiator or heat exchanger
(2) Electronic Thermostat (ESTAT) for the jacket water cooling system
(3) Engine block
(4) Jacket Water Aftercooler (JWAC) (front aftercooler core)
(5) Jacket water pump
(6) Engine oil coolerCoolant is pulled from radiator or heat exchanger (1) to water pump (5). From the water pump, coolant is sent through engine oil cooler (6). From the engine oil cooler, the coolant is sent to engine block (3). From the engine block, coolant is sent to ESTAT (2) and to the jacket water passage of the aftercooler (4). The coolant from the aftercooler is returned to the ESTAT. The ESTAT regulates the amount of coolant that flows through the radiator or heat exchanger to control engine temperature. The engine coolant that does not flow through the radiator is bypassed directly to the inlet of the jacket water pump.Coolant flows from the engine oil cooler into the water jacket at the front of the engine block. The coolant is directed toward the rear of the block through distribution manifolds. The distribution manifolds distribute the coolant to the water jacket for each cylinder. The coolant flows upward through the water jackets and around the cylinder liners. This area has the highest temperatures. As the coolant flows to the top of the cylinder liners, the coolant encounters a restriction due to smaller passages. The restriction causes the coolant flow to increase for improved cylinder liner cooling. Coolant flows from the top of the liners into passages that are cast into each of the cylinder heads. The coolant flows from the cylinder head back into the block and is returned to the front of the engine. As the coolant exits the front of the engine block, the coolant is directed through piping to the ESTAT and the after cooler core. Due to the restriction of the piping and after cooler core, a larger portion of the coolant flows to the ESTAT. The return coolant from the core is piped into a tee at the ESTAT.
Illustration 2 g03677762
(7) Three-way valve
(8) Electronic Fluid Temperature Control (EFTC)
(9) Stepper motorThe ESTAT utilizes a 3-way valve (7) that is electronically controlled by EFTC (8) to distribute the flow of the engine coolant. Engine temperate is inlet sensed by the engine jacket water pump outlet temperature sensor and outlet regulated by the EFTC to the radiator / heat exchanger. The outlet flow of coolant is directed by a piston that rides on a lead screw, which is driven by a stepper motor (9). For a cold engine, the EFTC bypasses the radiator/heat exchanger by sending the coolant directly back to the inlet of the water pump. As the engine warms, the EFTC controls the three-way valve to direct the correct amount of engine coolant through the radiator for coolingThe engine Electronic Control Module (ECM) transmits a temperature set point for the engine to the EFTC over the J1939 data link. The Engine Coolant Pump Outlet Temperature Sensor is used by the EFTC to detect the engine coolant temperature.