The Various Cooling System Components

Most people know what the cooling system of a vehicle does; it keeps the engine at the right temperature so that it doesn’t overheat. However, it’s one of the most misunderstood systems of a vehicle and has a variety of components. Familiarizing yourself with them can help you understand why some issues arise and when to visit a trusted mechanic for help.



The radiator’s core is primarily made up of aluminum tubes that are flattened with aluminum strips that go between the tubing. The fins transfer heat from the tubes into the air so that it can be carried away from your vehicle. Each end of your radiator core has a tank to cover the radiator ends. These tanks are usually made of plastic.

Modern radiators usually have tubes that run horizontally with the tank on each side. However, older models might have tubes that run vertically to the tank (top and bottom). Newer cars use aluminum for the core while older models primarily used copper with brass tanks.

Radiators with plastic caps have gaskets between the tank and aluminum core to help seal the system and prevent fluid leakage. Older cars with copper/brass radiators use a form of welding to seal the radiator.

Regardless of the tank material, they all have large hose connections, one of which is mounted at the top of the radiator so that coolant can come in and the other is mounted toward the bottom of the second tank to let coolant out. The top also contains the radiator cap.

The back of the radiator has electric radiator fans, which keep airflow moving into/out of the radiator when the vehicle is stopped or moving slowly. They are there to prevent the engine’s temperature from rising while sitting at a stop light or going through town.

Pressure Cap/Reserve Tank

When coolant gets hot, it is designed to expand. The cooling system is sealed, which causes more pressure. This is part of the design so that the pressure and ingredients in the coolant can reach a temperature higher than 250 degrees safely.

The pressure cap helps maintain the pressure of your cooling system. If it builds higher than the set point, a spring-loaded valve releases that pressure. When that happens, a tiny amount of coolant is released. The reserve tank can capture any excess coolant and store it, adding it back in when the engine cools off enough.

Water Pump

The water pump helps keep coolant flowing while the engine runs. It’s usually at the front of the engine and is designed to turn when the engine runs. It can be driven by a fan belt, serpentine belt, or a timing belt.

It’s usually made of cast aluminum or cast iron with an impeller, spinning shaft, and pulley system. It’s sealed so fluid can’t leak past the spinning shaft. Impellers draw coolant in using centrifugal force and send it to the engine block under pressure.


The thermostat is a valve used to measure the coolant’s temperature. It opens when the coolant is hot enough so that the coolant can go into the radiator. If the coolant isn’t hot, radiator flow is blocked, and the fluid goes through a bypass system so that it goes back to your engine. This system ensures that coolant keeps flowing until it reaches the right temperature. Flow is blocked by the thermostat, which means your engine gets to the right operating temperature faster and you get warm air inside your car on chilly days.

In the past, thermostats were calibrated to keep engine temps around 180 degrees Fahrenheit. However, they’ve been calibrated to stay above 192-195 degrees Fahrenheit since the 1970s.


The Various Cooling System Components

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