Advice Centre

Holding Icon Prevent Overheating

Coolant (a mixture of water and antifreeze) is pumped around the engine and cools it down by means of the car radiator. If the level of coolant gets too low, it can cause overheating and serious damage.The coolant should be renewed every two to five years.
Prevent Overheating

Checklist

Tools/materials needed:

  • Antifreeze suitable for your vehicle and weather conditions (check your vehicle handbook or Haynes manual for details)
  • Funnel or jug, Clean rag

Warning

Never undo the coolant filler cap while the engine is hot as there is a danger of scalding. Place a rag over the cap and unscrew it slowly to allow pressure to escape. Wash off any splashes of coolant from the skin (as it's poisonous) and from the car's bodywork (as it can damage paint).

How to Prevent Overheating
 

Step 1 - Check Coolant Level

Step 1

Most cars have a coolant reservoir with minimum and maximum level marks. With the engine cold, the coolant level should be between the two marks.

Step 2 - Top up Coolant

Step 2

If your coolant level is too low (below or near the lower mark), top it up using a 50/50 mixture of water and antifreeze (for normal driving conditions). You can use clean tap water in an emergency, but make up the antifreeze concentration afterwards). DO NOT overfill.

Step 3 - Refit Cap

Step 3

Refit the cap tightly afterwards and mop up any spillage.

Step 4 - Renew Coolant

Step 4

To renew the coolant, open the radiator drain tap or disconnect the bottom hose.

Step 5 - Flush the System

Step 5

If there is a cylinder block drain plug, unscrew it. Flush the system with clean water, or maybe a flushing compound.

Step 6 - Refill the System

Step 6

Close the drains and refit any hoses, then refill the system with the correct water/antifreeze mixture.

Shop online for your equipment.

Some cars have bleed screws that must be opened when refilling to avoid airlocks. Check your vehicle handbook or Haynes manual for details.

Haynes Hints

Haynes Hints

A leaking coolant hose can sometimes be patched up with a hose bandage. This will get you out of trouble until a new hose can be fitted. A leaking radiator will have to be replaced eventually, but adding a leak-sealing compound to the coolant reservoir will sometimes fix it for a while. A clogged-up radiator can cause overheating. Try using a cooling system flushing compound to clear it. If the engine starts to overheat when you’re driving and you can’t stop immediately, put the heater on (maximum heat, highest blower speed) to disperse some heat.

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