How do I top up my radiator?
... without scalding myself or blowing a gasketAt its peak, the temperature inside the combustion chamber of your car's engine can reach around 2500 degrees. That's a lot of heat for even the most sophisticated materials technology to handle and contain.
So an effective cooling system is imperative.
Let your car's radiator run low and you risk blowing a head gasket and, in extreme cases, warping a cylinder head. Once that happens, the engine will grind to a halt, and no amount of cranking the starter motor will get it running again.
Checklist
- Allow the engine to cool before removing the radiator cap,
- If the car is fitted with an overflow tank, check for coolant level visually,
- Don't remove the radiator cap if the car can be topped up from the overflow tank,
- Check the coolant level once a month as a general rule,
- Consult the service manual if in doubt as to how to check the coolant level,
- If in doubt, ask for expert help.
A radiator is a heat exchanger and forms part of the car's cooling system, which includes a water jacket in the engine block, the water pump and associated hoses. A fluid (usually water mixed with an anti-freeze chemical like ethylene glycol) pumped through the cooling system carries heat away from the engine by means of convection – contact with cooling air blowing through the capillary-like cores. The water pump keeps the coolant constantly circulating and the cooler fluid exits the radiator to return to the engine.
No coolant, no cooling.
Short of a major malfunction of the cooling system – a blown water pump or a holed radiator – maintenance is pretty straightforward. In between services it's simply a matter of checking the coolant level and topping it up, if necessary.
To start, purchase the right coolant and check the level in the overflow tank. The overflow tank is a plastic bottle with a black cap, placed close to the radiator in the engine bay.
If the level is below the minimum fill line on the tank, unscrew the cap and pour in enough coolant to reach the line. Refasten the cap, screwing it back in place by hand, tight enough for the engine-cooling system to repressurise, but not too tight.
Older cars don't have an overflow tank and the coolant has to be added to the radiator directly. The cap on the radiator has to be pushed down (like a kid-proof cap on a pill bottle) and turned anti-clockwise. Do NOT unscrew the cap of a radiator if the engine is still hot. The fluid inside will likely remain under pressure – having expanded within the confines of the cooling system. With all that pressure behind it, the coolant will burst out of the radiator with some energy – and if you're standing over the radiator at the time you may end up with a badly scalded face.
So this is an important safety tip: ONLY UNSCREW THE RADIATOR CAP WHEN THE ENGINE IS COLD – ambient temperature, in other words.
And if the car has an overflow tank, don't go anywhere near the radiator. Top up the overflow tank only.
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