Drip, drip. There’s a leak. And after a little investigation, you find it’s coming from your car’s radiator. 

While you might not know what a radiator does, you know a leak can’t be good. 

Engines create a lot of heat. To prevent them from overheating, the system is set up to pump coolant through your engine and back out, carrying heat away from the engine block. Coolant is used to take the heat generated in the engine, move it to the radiator, which in turn blows air across the liquid, cooling it down and sending the heat outside of the engine compartment. 

Radiators come in many shapes and sizes, but their primary function remains the same: it cools the coolant so the engine can stay cool and function well no matter how far you drive. 

Parts of a radiator

The radiator is made up of several major components:

Core – the core provides its primary function. It’s a large metal block with small fins that allow the coolant to vent heat away from the radiator, expelling it past the grill at the front of your vehicle. 

Pressure cap – the coolant system is constantly under pressure. Because it allows coolant to move heat without boiling, it creates an efficient system to transfer heat throughout. The pressure cap creates this pressure through a spring-loaded action; do not remove it while coolant is hot. 

Tanks – inlet and outlet tanks give the radiator space to move coolant from the hot parts inside the engine. 

Transmission coolant – cars also use the same coolant to cool the engine and cool the transmission. Transmission fluid moves through the engine in steel pipes, which surround heat and pulls heat away. This coolant is also cooled by the radiator. 

Why your car’s radiator may be leaking

With such an important job, finding a leak in the radiator is never a good thing. If you notice a leak, it may be from one of several things:

Corrosion

You only have to get near an engine to realize just how hot they get. Most car engines have a maximum heat capacity of 250 degrees Fahrenheit. That temperature applies to the coolant, as valves and other components can get even hotter the longer the car operates. 

That constant stress of pressure eventually wears and breaks down. Rust and corrosion begin to develop, allowing air and other contaminants to move in and cause problems. When the holes build up to a point where liquid can escape, leaks will occur and you’ll start to see coolant in and around the radiator. 

Gasket

The radiator gasket seals the connection between the radiator and the coolant tank. When this seal weakens, it allows fluid to leak. This is often a slow process, one you might not notice immediately. As it loses coolant, it causes the remaining liquid to work harder to get the job done. 

Hoses

In order to move coolant from the radiator to the engine, radiator tubes run through the system. As heat wears these down, it can cause them to weaken and become brittle. The connections between the radiator, water pump, and heater core are all vulnerable to heat, and are often the source of a leak. If you’ve noticed coolant puddling below your car, it’s one of the first places to look. 

Radiator cap

Though it’s not as common as the previous problems, occasionally a radiator cap will fail under the extreme pressure and heat it faces every day. It’s critical that a radiator cap maintains a tight seal. If not, the pressure will allow coolant to seep out from around the cap. This is the easiest and least expensive problem to fix. 

Water pump

The water pump is in charge of pushing coolant through the hoses to the engine compartment and back into the radiator. Without a functioning water pump, coolant won’t circulate to keep the engine cool. The water pump is belt-driven, hanging down near the ground where it attaches to a hose that feeds into the radiator. If this connection loosens, dirt or debris damages the pump, or the pump corrodes, it can spring a leak that results in a leak from the water pump. Any time a problem exists with the water pump, it can quickly build and allow the engine to overheat. 

Coolant reservoir

The coolant reservoir tank is made from plastic and has a chance of cracking or breaking down over time. It’s not always the tank that has a problem; also check the cap or hose connection points to see if they’ve been weakened, loosened, or broken. 

Head gasket

A worst-case scenario is the head gasket that separates the cylinder head from the engine block corrodes or cracks. Once this happens, it allows gas, coolant, and oil to mix together. This head gasket is under intense heat and pressure, and when it deals with this mixture, the head gasket blows and the engine is put in danger, possible failure. 

How do you avoid a radiator leak?

The easiest way to avoid a radiator leak is by bringing your car in for an occasional inspection. While coolant doesn’t need regular changing like motor oil, it should be checked periodically and flushed out as necessary. Check with your owner’s manual to determine how frequently a flush should occur. 

Ongoing maintenance includes checking coolant levels, checking for metal in the radiator, and inspecting hoses and connections to ensure they are all in optimal condition. Pay attention to your dashboard icons; a “check engine” light could be a warning for many problems, including coolant issues. Bring it in for an inspection as quickly as possible. 

Ensure your radiator is working well

Your vehicle’s radiator is essential to keep heat from building during operation. If the radiator isn’t working the way it should, it can cause severe damage to the engine by overheating. If you’ve ever seen a car by the side of the road, billowing heat from underneath the hood, it’s almost always a worn out radiator. 

The most common reason radiators malfunction is abuse or neglect. Want to keep it working well? Bring it in for an inspection from time to time. Add coolant as needed. Flush the system periodically. And fix any parts as they wear down or age. 

You’ll reduce your chances of being stranded by the side of the road.