BUSHING 5070387 - Caterpillar

Jacket Water Aftercooling
Illustration 1 g02373480
(1) Radiator or heat exchanger (2) Electronic thermostat for the jacket water cooling system (3) Temperature Control Module (TCM) (4) Engine block (5) Jacket Water Aftercooler (JWAC) (front aftercooler core) (6) Jacket water pump (7) Engine oil coolerCoolant is pulled from radiator (1) to water pump (6). From the water pump, coolant is sent through engine oil cooler (7). From the engine oil cooler, the coolant is sent to engine block (4). From the engine block, part of the coolant is sent to electronic thermostat (2) while the remainder is sent to JWAC (5). The coolant from the JWAC is returned to the electronic thermostat. The electronic thermostat regulates the amount of coolant that flows through the radiator in order 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.The 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 hottest temperatures. As the coolant flows to the top of the cylinder liners, the area of the water passages becomes smaller. This smaller area causes the coolant flow to increase for better 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 electronic thermostat and the JWAC aftercooler core. Due to the restriction of the piping and aftercooler core, a larger portion of the coolant flows to the electronic thermostat. The return coolant from the core is piped into a tee at the electronic thermostat.The electronic thermostat utilizes a 3-way valve that is electronically controlled by TCM (3) to distribute the flow of the engine coolant. For a cold engine, the TCM bypasses the engine block by sending the coolant directly back to the inlet of the water pump. As the engine warms, the TCM controls the electronic thermostat to direct the correct amount of engine coolant through the radiator for cooling.The Electronic Control Module (ECM) transmits a temperature setpoint for the engine to the TCM over the J1939 data link. A coolant temperature sensor is used by the TCM to detect the engine coolant temperature. The TCM and electronic thermostat provides for complete control of coolant flow for accurate engine temperature.The TCM commands a cooling purge cycle during engine start-up that removes trapped air from the cooling system. For the first 100 seconds after engine start-up, the TCM partially opens the 3-way valve to allow coolant flow through the radiator.