Auto Service Professional

APR 2016

Magazine for the auto service professional

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Circle 115 on Reader Service Card 38 | April 2016 The Chassis the turbo when the engine is shut off, but fne-tuning of the cooling system incor- porates a coolant shutoff solenoid valve, and a coolant bypass solenoid valve. These valves are controlled by the PCM using a low side driver and allow the PCM to calibrate and tailor the coolant fow in four distinct operating modes, or "phases," as Ford calls them. Phase 1: With an ambient temperature of 60 to 75 degrees F (16 to 24 degrees C) or above (this temperature range can be customized by the engineers) both the coolant shutoff and the coolant bypass solenoid valves are closed. The coolant does not circulate in the engine or through any other cooling circuits. This lack of fow sig- nifcantly reduces the warm-up time of the engine, and reduces start-up emissions and lowers fuel economy during warm-up. Phase 2: With an ambient temperature of 60 to 75 degrees F (16 to 24 degrees C) or below (again, this temperature range can be customized by the engineers), the coolant shutoff valve is opened; this allows cool- ant to circulate through the engine into the heater core, engine oil cooler, trans- mission oil cooler and around the bottom of the thermostat housing to warm the thermostat. Phase 3: When the coolant reaches 158 degrees F (70 degrees C) and the engine load is greater than 70% or the engine is revving greater than 4,000 rpm, the cool- ant bypass solenoid will open. This allows more coolant to fow from the engine to the thermostat housing, increasing the coolant fow through the engine, reducing cooling system pressure and better regulating tem- perature variations in the engine block. Phase 4: When the coolant reaches 180 degrees F (82 degrees C) the thermostat will open and allow coolant to fow to the radiator. The PCM can vary the temperature of the coolant coming in contact with the thermostat by using the coolant bypass solenoid. This results in a variable oper- ating temperature zone of between 180 degrees F (82 degrees C) and 198 degrees F (92 degrees C). This allows higher operating

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