Car cooling system: why engine coolant is so important

Radiator cap
  • Cooling system checks should be part of routine maintenance
  • Check your coolant level every time you refuel
  • Never remove the radiator cap on a hot engine
  • If your car has overheated, pull over and call for assistance

Many engine failures are caused by neglecting the car’s cooling system. This is even more important in the Australian climate. Proper maintenance and regular checking of your engine coolant levels can save you from costly engine damage.

How to check your engine’s coolant level

Make a habit of doing a quick visual check of the coolant level in the overflow bottle each time you fill up with fuel. If the level is low, ensure you don’t remove the radiator filler cap until the engine is cool – it usually takes a few hours after a drive.

If you’re topping up or changing the coolant yourself, check the owner’s manual, or call NRMA motoring advice on 13 11 22, for the correct type and quantity of coolant to use, as well as the right method. You can also visit an NRMA car servicing store for advice.

What if I have to continually top up the engine coolant?

If you have to top up the coolant level often, and you’ve noticed a puddle under the car, it could be that the radiator or one of the hoses has a leak.

If there is no sign of coolant coming out of the engine, it could be leaking inside the engine.

An external leak is usually easier to fix than an internal one, a sign that could point to a more serious problem. Either way, it’s important to take your vehicle to a mechanic as soon as possible to prevent further problems.

As well as checking the coolant level, keep an eye on the temperature gauge near the speedometer. If the needle rises out of its normal range, this will often trigger a warning light or tone and could also signal a cooling system problem. Stopping the car somewhere safe, and calling for roadside assistance, could save your car from expensive engine damage.

How does my car’s cooling system work?

The cooling system removes about a third of the engine’s waste heat by circulating coolant through the engine. Even in today’s fuel-efficient engines, only around a third of the heat produced during combustion is converted into mechanical energy to drive the car. The rest is carried away by the exhaust and cooling systems.

The main components of a car cooling system

  • Radiator with pressurised cap
  • Overflow bottle
  • Thermostat
  • Cooling fan

Car cooling systemCoolant is a mixture of water and chemicals designed to prevent corrosion inside the engine. If you’re driving in cold conditions, you may need to add anti freeze to the cooling system. Always follow the vehicle manufacturer’s directions when using anti freeze and coolant. 

A pressurised radiator cap raises the boiling point of the coolant, which is why you should never remove the radiator cap on a hot engine. The overflow bottle lets the coolant expand when it’s hot.

The cooling fan provides air flow through the radiator when the car is not moving, such as when you’re stuck in traffic.

The cooling system maintains the engine at an ideal operating temperature using a thermostat. The thermostat restricts the flow of coolant when the engine is cold, to help it get to this efficient working temperature quickly.

Need some help? Book a car service

Leaks, incorrect or low coolant level, or faulty cooling system components can quickly turn into even bigger problems.

A regular service at a reputable mechanic – and routine coolant level checks – will help catch cooling system problems before they become serious.

If you’re not confident carrying out cooling system maintenance on your own, your local NRMA car servicing or mobile mechanic can help.