Have you ever popped your car’s bonnet after a long drive and felt the heat radiating from the engine? As hot as that feels, the combustion chambers inside the engine can reach 4,500 degrees Fahrenheit —nearly twice stainless steel’s melting point. But thanks to your radiator, your engine can withstand temperatures that should cripple it. What does a radiator do, and how does it work?
What does a radiator do?
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.
Core
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
Coolant, 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.
Hoses
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.
Thermostat
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.
How to tell if you need a new radiator
A radiator is critical equipment for every modern vehicle. Attempting to drive with a damaged one will lead to short trips and hefty repair bills. Here’s what it looks like if your radiator is starting to have trouble or is already on its way out. If you notice any of these things, get your car checked out ASAP.
Overheating
High temperatures are often the first sign that something is up with your radiator. This is because neglect or unseen damage can lower coolant levels, and then the system doesn’t have enough fluid to cool the engine. You’ll notice the temperature gauge rising and reduced performance. Hopefully, you’ll get a check engine light before anything expensive breaks.
Damaged fins
The aluminium radiator provides greater surface area than flat metal, transferring more heat into the air. If the fins take damage from rocks or a minor fender-bender, the radiator loses effectiveness. A few bent fins are fine. But if you’re inspecting a used car with heavily damaged fins, then keep an eye on the temperature gauge on your test drive.
Leaking coolant
If you notice a puddle of green fluid under your vehicle, you could soon have a radiator issue. The cooling system is sealed and should not leak. Cracks can happen in the radiator inlet or outlet, or coolant hoses can become brittle and cracked with age.
Dirty/sludgy coolant
Very few systems in a vehicle are maintenance-free. Leave your engine oil in place too long and it becomes filthy and sludgy. The same is true of the cooling system. That coolant, left for years, becomes corrosive. The rust-inhibitors stop working as the coolant starts wearing down the engine’s internal parts. Change this coolant ASAP.
Engine smoke
Low coolant can cause an overheated engine, which causes metal parts to expand at different rates, in turn causing damage like broken head gaskets. Coolant gets into the engine and burns off as sweet-smelling white smoke. This one is serious, so just pull over and turn off the engine. You’ll need to have the car towed to a shop.
Nelson Xavier Ssenyange
Team Leader
Germax Autos, Spares & Garage Ltd
Lukade Road, Naalya
0779250886/0752088734