Automotive Engine Cooling System Components

Cooling System Components

Water Pump

3.1. WATER PUMP: Drives the cooling liquid through the circuit. It is centrifugal and receives rotational movement from the crankshaft via a belt. The engine generates more heat when speed increases, so the flow rate delivered by the pump must increase to provide sufficient cooling capacity. It is mounted on the block, at the height of the cylinders, to drive the liquid coming from the radiator into the engine. It is driven by accessory belts or the timing belt. DRIVE:

• Poly-V belt
• V-belt

Radiator

3.2. Radiator: A liquid-air heat exchanger. Heat is carried by the coolant through the engine and is transferred in part to the air as it passes through the radiator, which is optimally positioned to receive the airflow when the vehicle moves. Additionally, a fan provides an airstream. The radiator consists of a core and two tanks; the core is formed by thin tubes that connect both tanks, and fins are welded between the tubes.

TYPES:

• Vertical flow: A tank above and one below; the liquid flows vertically up and down.
• Crossflow: Tanks on the sides and the liquid moves horizontally. It adapts to low-front (low-profile) designs and is commonly used today.

@ Circuit Pressurized: The circuit is sealed to prevent air ingress. The fluid expands when heated and contracts when cooled; an expansion tank is incorporated to accommodate this. Entry and exit are controlled through a pressure valve and a vacuum (depression) valve found in the radiator cap or expansion tank.

Thermostat

3.3. THERMOSTAT: When cold, it shuts off water flow to the radiator so coolant circulates only through the engine to warm up quickly. When the engine reaches operating temperature, the thermostat opens, allowing water into the radiator. It consists of a wax capsule that expands when heated; the expansion compresses a rubber element that pushes a rod, which overcomes the spring force and opens the valve.

Fan

3.4. FAN: The fan delivers an airflow through the radiator to exchange heat with the coolant. Its mission is to maintain the thermostat temperature stable, independent of engine revolutions.

Thermocontact: An electrical system with a bimetallic element; when the engine reaches about 85ºC the circuit closes, energizing the relay and starting the fan.

ELECTRICAL: The fan is driven by an electric motor whose power depends on the fan characteristics. It typically engages between 90 and 98ºC and turns off between 82 and 90ºC; a difference (hysteresis) of 5–8ºC prevents excessive cycling.

Viscous coupling: Uses a silicone fluid whose viscosity changes with temperature; at low temperature it is effectively locked and when heated it allows relative motion to modulate fan drive.

ASSEMBLY: Depending on cooling needs, engine type and equipment, one or two fans are mounted, and they may be single-speed or two-speed (using two thermal contacts). Configurations include:

• One fan, one speed
• One fan, two speeds
• Two fans (two-step functions)
• Fan driven by belt (united with accessory belt)

INDICATOR Temp: A resistive sensor whose ohmic value varies with temperature. It controls the temperature indicator and warning lights on the instrument panel; sensors are often located near the thermostat.