Powertrain Secondary Cooling System
Powertrain Secondary Cooling System
System Overview
NOTICE: Always fill the cooling system with the same type of coolant that is present in the system. Do not mix coolant types. Mixing coolant types can result in cooling system damage.
NOTE: During normal vehicle operation, Motorcraft Specialty Orange Engine Coolant may change color from orange to pink or light red. As long as the engine coolant is clear and uncontaminated, this color change does not indicate the engine coolant has degraded nor does it require the engine coolant to be drained, the system to be flushed, or the engine coolant to be replaced.
The secondary cooling system uses coolant flowing in a circuit separate from the primary engine cooling system. This system cools the exhaust gasses for the EGR system, the transmission fluid, the fuel, and the air charge entering the engine. A secondary engine-driven coolant pump provides for coolant flow. A secondary, 2-stage radiator is mounted in front of the primary engine cooling system radiator. Two thermostats, one mounted on each side of the secondary radiator, operate independently to regulate the temperature of the coolant flowing to the various components.
System coolant provides freeze protection, boil protection, cooling efficiency and corrosion protection to the cooling components. In order to obtain these protections, maintain the coolant at the correct concentration and fluid level in the degas bottle.
When adding engine coolant, use a 50/50 mixture of engine coolant and distilled water. A coolant concentration of 50% will provide freeze point protection down to -36°C (-33°F).
To maintain the integrity of the coolant and the cooling system:
- NOTICE: With the engine cold, fill vehicles to within the cold fill range shown on the degas bottle. This fill level will allow for coolant expansion. Overfilling the degas bottle may result in damage to the pressure cap, which can cause the system to overheat.
Add Motorcraft(R) Specialty Orange Engine Coolant. Do not mix coolant types. Mixing coolants may degrade the coolant's corrosion protection.
- Do not add alcohol, methanol, brine or any coolants mixed with alcohol or methanol antifreeze. These can cause damage from overheating or freezing.
- Do not mix with recycled coolant. Use of such coolants may harm the cooling system components. Do not mix coolant types.
Component List
The secondary cooling system components include the following:
- Degas bottle
- Coolant pump (mounted on the upper RH side of the front of the engine)
- Radiator (mounted in front of the primary cooling system radiator)
- Two thermostats (one mounted on each side of the radiator)
- EGR cooler (mounted on top of the RH valve cover)
- Transmission fluid cooler (mounted near the front of the engine, on the RH frame rail)
- Charge Air Cooler (CAC) (mounted on the LH side of the front of the engine compartment)
- Fuel cooler (mounted on the LH frame rail near the transmission)
- Hoses and tubes connect the various components
Coolant Flow Diagram
NOTE: Coolant temperature will vary with ambient temperature and load. Temperatures shown are for ambient temperature of 38°C (100.4°F). Black arrows indicate maximum temperature over 90°C (194°F), shaded arrows indicate maximum temperature approximately 60°C (140°F), white arrows indicate maximum temperature under 45°C (113°F).
System Operation
The coolant flows from the degas bottle to the coolant pump. The coolant pump delivers the coolant to the tank attached to the LH side of the radiator, via a hose and tube assembly. The radiator is divided horizontally into two separate sections, the top section comprising approximately two-thirds of the radiator and approximately two-thirds of the tank attached to the LH side of the radiator. The lower one-third of the radiator and the lower one-third of the tank attached to the LH side of the radiator comprise the lower section. The tank attached to the RH side of the radiator connects the two sections.
Two thermostats control the coolant flow through the radiator and have different opening temperatures. Refer to Specifications for thermostat opening temperatures.
The thermostat on the RH side of the radiator controls coolant flow to the transmission fluid cooler and the EGR cooler. When the thermostat is closed, coolant is delivered to the thermostat housing via a connection to the coolant pump-to-radiator hose and tube assembly. The coolant then flows out of the thermostat housing via two separate hoses to the transmission cooler and the EGR cooler. When the thermostat is opened, the coolant connection from the coolant pump-to-radiator hose and tube assembly is blocked, and the coolant entering the tank on the LH side of the radiator is allowed to flow through the top two-thirds of the radiator and then to the transmission cooler and the EGR cooler. Separate hoses leading from the EGR cooler and the transmission cooler return the coolant to the degas bottle.
The thermostat on the LH side of the radiator controls coolant flow to the Charge Air Cooler (CAC) and the fuel cooler. When the thermostat is closed, coolant flows from the top tank on the LH side of the engine to the thermostat housing, and then out of the thermostat housing via a single hose. A "Y" connection allows the coolant to flow through separate hoses to the CAC and the fuel cooler. When the thermostat is opened, the coolant entering the thermostat housing from the upper tank is blocked, and the coolant flows through both the upper and lower sections of the radiator before flowing to the CAC and the fuel cooler. The coolant flows from the CAC and the fuel cooler via separate hoses to a "Y" connection, and then via a single hose to the degas bottle.
The fuel cooler cools the excess fuel being returned to the fuel control module from the fuel rail. For additional information, refer to Fuel Charging and Controls - Fuel Cooling System Fuel Cooling System.
The EGR cooler is part of the engine emissions. For additional information, refer to Engine Emission Control Engine Emission Control.
The CAC is part of the air intake. For additional information, refer to Intake Air Distribution and Filtering Intake Air Distribution and Filtering.
The transmission fluid cooler is part of transmission cooling. For additional information, refer to Transaxle/Transmission Cooling Transmission Cooling.