Angie's LIST Guide to
What does a radiator do?
A radiator is an essential component in any internal-combustion engine. Your car’s engine relies on coolant passing through the engine block to absorb and transfer heat (represented in red below). Heat removal is achieved by forcing the coolant, which is actually a water-coolant mixture and also known as anti-freeze, through the vehicle’s radiator. Without this temperature regulation, the engine would overheat, causing catastrophic damage to engine components.
The radiator removes the heat within the coolant by forcing it through a series of tubes within the compact space of the radiator itself. Produced by vehicle movement or an electrically or pulley powered fan, incoming air rushes over the tubes, carrying away heat as it passes. This creates a greater amount of surface area the air comes in contact with, the radiator tubes are attached to radiator fins, which appear as a grill-like pattern on the radiator’s larger surface.
Once the hot coolant has passed through the radiator and cooled down (shown in blue below), it is directed back through the engine core and the heat absorption and removal cycle begins again.
Fan –Powered by electricity or driven by the engine’s drive belt, the fan ensures that the radiator adequately dissipates heat even when the vehicle is not in motion.
Heater core – Used to heat the interior of the car’s cabin, the heater core allows hot coolant from the engine to enter a series of tubes. A fan blows air over the tubes, allowing heated air into the cabin.
Pressure cap – A radiator system is a pressurized, closed loop. If and when necessary, the pressure can be relieved via the pressure cap, which may also be removed for inspection or topping off fluid in the radiator itself. Never open the pressure cap when a vehicle engine is hot, as pressurize steam can cause severe burns.
Radiator – The main component of a vehicle’s cooling system, a series of compactly wound tubes attached to fins. When coolant enters the tubes, air is blown by the vehicle movement or a powered fan, radiating heat away and causing the coolant to become cool again.
Reserve tank – Contains a reserve supply of coolant that can enter the radiator system as needed. Always check your car’s coolant level from the reserve tank and not the pressure cap.
Thermostat – The thermostat, much like your home, measures the temperature of the radiator system. However, in an automobile, it acts as a valve that ensures optimum cooling performance by only allowing the system to cycle hot coolant into the radiator under specific temperatures
Transmission cooler – Some vehicles, such as those used for heavy duty applications like towing, may feature a transmission cooler near or on the radiator. It acts much in the same way as a radiator does, but serves to reduce the temperature on the transmission.
Water pump – Ensures that coolant pumps through the engine block and coolant system.
(Illustration by Garrett O' Sha)
How does a radiator work?
Like any system that contributes to your vehicle running smoothly and dependably, your car’s radiator needs occasional routine maintenance.
Coolant level checks
It’s a good idea to check the coolant level in your car radiator’s reserve tank at least every six months, or every time you change your oil. Always check the coolant level when the vehicle engine is cool and always check via the coolant reservoir, not the radiator cap. Severe steam burns may result if you attempt to unscrew the pressurized radiator cap when the engine is warm.
If the coolant level is low, top it off and keep an eye on it and your vehicle’s dashboard temperature gauge. If the radiator system is losing coolant on a continuous basis, it almost certainly has a leak.
A radiator leak, large or small, should be cause for immediate action, such as taking the vehicle to a qualified service center. Radiator or coolant leaks can be easy to spot if enough fluid has leaked out, due to the fluorescent green, orange or bright red coloring added to radiator fluid. Another symptom of a radiator leak is dropping coolant level in the coolant reservoir or engine temperature rising slowly over time.
Leaks may come from a number of locations, including holes in the radiator tubing, connection hoses, the water pump and other components, so if you suspect a leak, have a qualified mechanic perform an evaluation to find the leak source and correct it.
One of the most important maintenance items you’ll need to perform, or have a trusted auto service shop perform, is a radiator flush. During a radiator flush, all of the radiator system's existing coolant is removed from the system, the system is flushed out and then refilled with the correct amount of new coolant.
Radiator coolant is actually a mixture of about half water and half chemical additives, the additives helping the coolant achieve a higher boiling point and prevent it from freezing. Although many coolant products also feature anti-corrosive additives, the water within the coolant system can eventually cause the inner workings of the radiator system to rust. A radiator flush costs relatively little and if performed every two years, or as recommended by your manufacturer’s service schedule, helps ensure that the radiator coolant isn’t corroding the system.
A number of symptoms can signal the need for new radiator. As mentioned in the section above, regularly checking coolant levels and addressing coolant leaks are two proactive ways to avoid radiator problems.
If you notice the temperature gauge on the instrument cluster, or warning lights for vehicles with more advanced diagnostic systems, indicating a higher than normal temperature, it’s imperative to avoid further driving if possible. Pull over or park at the safest place possible and turn off the car. Call a qualified auto service shop and ask them about what the next steps you should take, including how severe the problem may be and whether you will need a tow truck. Continuing to drive with an overheated engine can cause severe damage that will likely require thousands in repairs.
If it’s not possible to pull over, if you’re driving in a highway construction zone for example, turn on the heater to try to pull as much heat away from the engine as possible. Other signs that your radiator has overheated are a burning or “smell” emanating from underneath the hood, and intermittent loss of engine power or a complete loss of power. If you notice these signs, it’s likely that your engine has already suffered damage from overheating.