Flushing the coolant system removes old coolant, rust, and deposits, helping prevent overheating and extending engine life. This is a more involved job than a simple top-up, but it can be done at home with care.
Correct type of new coolant (check owner’s manual)
Distilled water (recommended)
Large drain pan/container
Funnel
Socket set or spanner
Hose pipe (optional, for flushing)
Jack and axle stands or ramps (if needed for access)
Gloves and rags
Let the car cool completely (at least 1–2 hours after driving).
Never open the cooling system when hot—pressurised coolant can cause serious burns.
Open the bonnet.
Place a drain pan under the radiator drain plug (or lower radiator hose if no drain plug is available).
Open the coolant reservoir cap (this helps it drain faster).
Open the drain valve or remove the lower hose.
Allow all coolant to drain completely.
You have two common options:
Basic water flush:
Close the drain plug.
Fill the system with distilled water.
Start the engine and run it for 5–10 minutes (heater on full hot).
Turn off engine, let it cool, then drain again.
More thorough flush:
Use a radiator flush solution (follow product instructions).
Run engine as directed, then drain.
Repeat until water runs clear.
Ensure the drain plug is tightened.
Reconnect any hoses that were removed.
Make sure everything is secure before refilling.
Mix coolant with distilled water if required (many are 50/50 pre-mixed or concentrate).
Slowly fill the radiator (if accessible) or coolant reservoir.
Fill to the MAX line.
Air pockets can cause overheating.
Start the engine with the radiator cap off (if applicable).
Turn heater to maximum heat.
Let engine idle.
Watch for bubbles escaping.
Top up coolant as the level drops.
Once bubbles stop and level stabilises, replace the cap.
(Some cars have bleed screws—follow the manual if present.)
Inspect hoses, radiator, and drain point.
Let the engine reach operating temperature.
Turn off and recheck coolant level when cold again.
Top up if necessary.
Most manufacturers recommend a coolant change every 2–5 years depending on type.
Always use the correct coolant specification—mixing types can cause damage.
Keep coolant off painted surfaces; it can cause damage if not cleaned quickly.
Never open a hot cooling system.
Dispose of old coolant properly—it's toxic to animals and the environment.
If the engine overheats after a flush, stop driving and check for air locks or leaks immediately.