The radiator in your vehicle is designed to remove the heat generated by the engine to the air in order to regulate the engine temperature and prevent overheating. The engine block and cylinder head contain passageways filled with coolant (usually a mixture of water and glycols). The coolant is pumped around the car engine by the water pump and absorbs the heat generated in the engine by the combustion process. When it reaches the radiator the coolant flows through a series of tubes where it is transferred to the outside air via fins. The fins greatly increase the surface area of the radiator to make heat transfer more efficient.

An engine needs to burn fuel to run, a process which naturally produces an immense amount of heat and requires the engine to be cooled as much as possible so that the pistons do not break down and destroy the entire system. This is where the radiator, which is part of the engine’s cooling system, comes in.

• The coolant in an engine is passed through tubes that comprise the majority of the radiator, where it can lose the heat it picks up to the atmosphere before returning to the engine.
• It enters the pipes in an overheated state, causing it to become highly pressurised (aided by turbulence inside the radiator pipes), at which point the radiator cap opens at a predetermined pressure point.
• This releases the heat and allows any excess coolant to escape into an overflow tank attached to the side of the radiator.
• That coolant is then returned to the radiator when its temperature has sufficiently lowered.

Although there are slight variations to the radiator and cooling system in general from model to model (especially in older cars versus newer models), this is the process that the majority of systems employ, and knowing how they work will help you when it comes to diagnosing any issues that might occur with them.

FREQUENT ENGINE OVERHEATING
Given that the radiator is designed to cool the engine down, a frequently overheating engine could well be a sign of a leaking radiator. Keep an eye on the engine temperature (or general internal temperature) gauges and make sure that the needle isn’t drifting into the red too often.

PUDDLE UNDERNEATH THE ENGINE
You are more likely to spot a leaking radiator when the car is parked and a puddle forms underneath it. If the liquid is green and slimy then it will be coolant, indicating that a leak has sprung from somewhere. Do not touch it, as it is hazardous – clean it up while wearing protective clothing as soon as possible, especially if you have young children or pets.

DROP IN COOLANT LEVELS
Coolant levels tend to drop even when the radiator isn’t leaking – this happens naturally and the coolant should be replaced as and when it needs it. If the coolant levels take a drastic fall, though, take the car to a mechanic to confirm that the radiator is leaking (assuming there are no other visible symptoms that will allow you to confirm it yourself).

STEP-BY-STEP GUIDE

1. Ensure the engine is completely cool so you don’t burn yourself while you work – wait at least two hours after turning it off to be on the safe side.
2. Clean the radiator with soapy water and a brush.
3. Position the drainage pan underneath the radiator drain valve (or petcock). Pull the petcock handle to release the coolant.
4. Double-check the radiator cap and the two hoses that take the heated coolant out of the system and flush the system with cold coolant for wear and tear, and take the opportunity to replace them if necessary.
5. Rinse the radiator by filling it with water and pulling the petcock again to let it run out.
6. Add new coolant via the radiator cap in the same way (but don’t pull the petcock out).
7. Bleed the radiator by leaving the radiator cap off and running the engine with the car remaining stationary for fifteen minutes. This allows air voids to exit and should subsequently mean that more coolant can be added.