A radiator cools the engine using cool air to remove heat from the hot liquid coolant. The radiator is part of a sealed cooling system and is essentially a heat exchanger between hot coolant coming from the engine and the much cooler outside air. In short, it keeps the engine from destroying itself from excess heat.
Parts of a radiator
A radiator usually gets replaced as a single unit. But there are several key parts to a radiator, and even more in the cooling system. Here’s how it all works together to keep your engine cool.
This is where the cooling happens. The aluminium core is a long series of tubes that carries hot coolant. Heat is dispersed as air flows over the tubes and a dense network of fins. Aluminium is used for both its heat dissipation properties and relatively light weight. By the time the coolant makes it through all the tubing in the core, airflow has pulled away one-third of the engine’s heat.
- Inlet/outlet tanks
Modern cars usually have plastic pipes/tanks feeding the core. This is most noticeable at the inlet and outlet. Where the coolant enters or leaves the core, you see the change in material from aluminium to plastic. The plastic has a high strength-to-weight ratio and is great for heat dissipation. But it’s difficult to repair if there is a leak.
- Pressure cap
Also called a radiator cap on older cars, this helps improve cooling-system efficiency. Pressure increases water’s boiling point, so a pressurized cooling system won’t boil at 212 degrees. With vehicle engines normally operating between 195 and 220 degrees, the pressure cap keeps the engine from boiling away coolant every time you drive.
Coolant, also often called antifreeze, is the liquid that circulates in the cooling system. It absorbs heat from the engine then releases it in the radiator. Coolant is made up of several compounds, but it’s mainly water. In addition to preventing freezing, coolant also keeps vital engine parts from rusting.
- Transmission cooler
A transmission cooler looks like a miniature radiator, with a series of tubes curving behind aluminium fins. It sits in front of the radiator and works on the same premise cooler air draws heat from liquid coolant. The difference is that the hot liquid is transmission fluid, which when cooled and returned to the transmission case helps extend transmission life.
Flexible rubber hoses connect the radiator to the engine block. One is an inlet, carrying hot coolant from the engine. The other is the outlet, returning the cooler fluid to the engine for another cycle. If you’re having cooling issues, hopefully it’s just a failing coolant hose. These are cheap and easy to replace.
The thermostat is a small device in the cooling passages that maintains the proper coolant temperature. On start-up, the thermostat stays closed, keeping the coolant inside the engine while it warms up to operating temp. The right amount of heat makes the thermostat open, allowing full circulation of the cooling system.
- Coolant reservoir
If the cooling-system pressure exceeds the cap’s pressure rating, the excess pressure forces coolant through the overflow tube into the coolant reservoir. Once the system cools down after shutoff, it pulls this reserve fluid back into circulation. In most modern cars, the reservoir is where you add coolant, instead of directly to the radiator.
- Water pump
A water pump is an impeller mounted to the front of the engine block. When it spins, it forces coolant through the engine’s passages and the rest of the cooling system. Water pumps are usually mechanically driven but can be electronically driven in modern cars.
- Radiator fans
Cooling fans, or radiator fans, are exactly what the name sounds like. These fans sit behind the radiator and help pull cooler air over the radiator fins, increasing cooling-system effectiveness. The fans sit inside the radiator shroud that also helps direct air. Older cars with carburettors will likely have an engine-mounted mechanical fan doing this task.
Nelson Xavier Ssenyange
Germax Autos, Spares & Garage Ltd
Lukade Road, Naalya