A radiator is a key component of an engine cooling system. It disperses excessive heat from the engine into air, preventing it from overheating. 

A leaking or malfunctioning radiator can become a source of serious engine problems and even cause its complete failure if ignored. That’s why you should be aware of the most common signs of a faulty radiator:

Coolant leaks

If your radiator gets cracked or rusted, coolant that circulates throughout the radiator will leak out.

Engine overheating

A leaking radiator will cause a loss of engine coolant while the engine is running. When the coolant level reaches its critical value, the engine will overheat due to a lack of coolant.

Warning lights are on

If the coolant level drops down and the engine overheats, your temperature gauge will show high readings. Your warning lights and the check engine light will also come on.

Malfunctioning cabin heater

Your cabin heater core relies on the coolant to warm up your passenger area. If the coolant level reduces due to a leaking radiator, the heater core will experience a lack of hot coolant and malfunction.

Coolant mixes with the transmission fluid

Some radiators come with a built-in transmission fluid cooler. If the cooler inside such a radiator cracks and leaks, the transmission fluid and coolant will mix together.

What is a radiator?

A typical radiator is an arrangement of tubes and fins surrounding the tubes. On one side of this system there is an inlet tank, while the opposite side features an outlet tank. Both tanks are connected to the engine via cooling hoses. 

When the coolant temperature reaches approximately 80'C (176'F), the thermostat opens allowing hot coolant to enter the inlet tank. It flows through the set of tubes where it cools down and then exits via the outlet tank. When the coolant circulates through the radiator, incoming air enters through the front grille, absorbing heat from hot tubes and fins. If your car is moving slowly while your engine is getting overheated, your radiator fan is activated, forcing air through the radiator.

When your engine is running, your radiator is subjected to high temperatures and pressure. The latter may destroy the radiator if not controlled. For this reason, the radiator features a special cap with a built-in valve that opens when the tank pressure exceeds the set point pressure, protecting the radiator from damage. 

Vehicles with an automatic transmission usually come with a transmission fluid cooler built in the radiator. The cooler is used to cool down transmission oil to prevent the powertrain from overheating.

How can I fix a bad radiator?

A cracked or leaking radiator is not repairable. It should be replaced as soon as possible to prevent engine overheating and possible damage. After replacing the radiator, the cooling system should be flushed to remove any contaminants that could remain in the cooling system. In some cases, the radiator hoses and thermostat replacements are recommended. When everything is done, the cooling system must be topped up with fresh coolant and checked for coolant leaks.