Ford Fiesta: Engine Cooling - 1.6L EcoBoost (132kW/180PS) – Sigma / Engine Cooling - System Operation and Component Description. Description and Operation

System Operation

Engine coolant flows primarily from the engine to the radiator circuit and back to the coolant pump. Coolant is sent from the coolant pump through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core and turbochargers with coolant. The coolant pump, operated by engine rotation through the accessory drive belt, circulates the coolant. The coolant thermostat is a control valve actuated by coolant temperature. When the thermostat is closed, coolant flow bypasses the radiator circuit and returns to the coolant pump. When the thermostat is opened, coolant flows through the radiator circuit to transfer engine-generated heat to the outside air.

The degas bottle holds surplus coolant and removes air from the cooling system. It also allows for coolant expansion and system pressurization, replenishes coolant to the cooling system and serves as the location for service fill.

The thermostat monitor is a function of the PCM and is designed to verify correct thermostat operation. The monitor executes once per drive cycle and has a monitor run duration of 300-800 seconds. If a malfunction occurs, DTC P0125 or P0128 sets, and the MIL illuminates.

The engine's cooling circuit consists of an additional coolant bypass solenoid valve and coolant shutoff solenoid valve. Using these two valves, the coolant flow through the engine is specifically restricted or stagnated in the warm-up phase. This restriction of the coolant flow makes it possible for the engine components to warm up faster. The result is a significant reduction in the emissions of harmful pollutants and an improvement in fuel economy (i.e. reduced friction) during the warm-up phase. Both solenoid valves are controlled by the PCM .

The following input parameters are used to do this:

• Coolant temperature
• Ambient air temperature
• Engine speed
• Engine load
• Status of the air conditioning system

Warm-up regulation is performed in four phases. Phase 1 or 2 occurs after initial engine start-up depending on the ambient air temperature.

Phase 1:

During an initial engine start-up with an ambient temperature is 60-75F (16-24C) or warmer (calibratable) the coolant shutoff solenoid valve closes and the coolant bypass solenoid valve remains closed. With both valves closed the coolant is stagnant and does not circulate in the engine (cylinder block and cylinder head) or through any other cooling system component to significantly decrease the engine warm up time. This reduces emissions and fuel consumption during warm-up.

Phase 2:

During an initial start-up with an ambient temperature 60-75F (16-24C) or cooler (calibratable) the coolant shutoff solenoid valve remains open. This allows engine coolant to circulate through the heater core providing cabin heat to the customer. When the coolant shutoff solenoid valve is open, the coolant circulates through the engine (cylinder block and cylinder head), heater core, engine oil cooler, transmission oil cooler, turbo, and degas bottle. Coolant is also routed into the thermostat housing which initiates the warm-up phase of the thermostat.

Phase 3:

The coolant bypass solenoid valve is energized and opens when engine coolant reaches (158F) 70C and the engine load is greater than 70% or engine speed is greater than 4,000rpm. When the coolant bypass solenoid valve opens coolant is routed through a coolant between the engine block output and thermostat housing. The opening of this coolant circuit increases the coolant flow rate through the engine block which reduces cooling system pressure and temperature fluctuations in the engine block.

Phase 4:

At about (194F) 90C, the thermostat opens and the coolant is routed through the radiator. However, the thermostat opening temperature is partially variable via the coolant bypass solenoid valve. The temperature around the thermostat and its expansion element is the total of the coolant temperatures entering the thermostat housing. Targeted actuation of the coolant bypass solenoid valve allows increased flow of coolant from the engine block to contact the thermostat element and allows an actual coolant temperature of between (194F) 90C and (212F) 100C to be set. During part throttle driving, fuel consumption depends heavily on coolant temperature. Closing of the coolant bypass solenoid valve makes it possible to drive with a higher coolant temperature during part throttle conditions.

Component Description

Coolant Shutoff Solenoid Valve

The coolant shutoff solenoid valve is an electrically controlled solenoid to allow or block the flow of engine coolant. This electrically controllable valve is normally open when not energized. The valve receives a fused 12V B+ supply when the ignition is in the run or start position and is grounded by the PCM via a low side driver. The PCM monitors the solenoid and circuits for electrical faults and sets an appropriate DTC .

Coolant Bypass Solenoid Valve

The coolant bypass solenoid valve is an electrically controlled solenoid to allow or block the flow of engine coolant. This electrically controllable valve is normally closed when not energized. The valve receives a fused 12V B+ supply when the ignition is in the run or start position and is grounded by the PCM via a low side driver. The PCM monitors the solenoid and circuits for electrical faults and sets an appropriate DTC .