Overheating can ruin a car engine very quickly, so if the temperature gauge starts edging up near the HOT or red section, take immediate action to cool the engine down again.
Turn on the heater to maximum and switch the blower fan on (it draws off engine heat). if you stop for a minute or more in traffic or at lights, shift into Neutral and rev the engine at a fast idle speed.
If this doesn't stop the temperature rise, get off the road at your first opportunity. Raise the bonnet (but be careful-the bonnet and under bonnet areas are hot) and see if there is something obviously wrong, such as a snapped fan belt or water pump belt, a broken fan, a coolant leak, or insects or other debris covering the radiator.
If there are no obvious reasons for overheating, wait an hour for the engine to cool, take off the radiator cap and check the coolant level in the radiator. If the water level is low, let the engine idle while you top it up with coolant (plain water will do). As soon as possible, have the system drained and inspected for radiator cracks or other flaws before it is filled with the appropriate coolant mixture (water and anti-freeze solution).
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