Fresh 50/50 antifreeze is not just about frost — it carries the corrosion inhibitors that keep an iron block and brass/copper radiator alive.
Step by step
- 01
Only open the system COLD
Never open the radiator cap on a hot engine — a scalding jet of coolant WILL come out. Let the engine cool completely.
- 02
Drain the block and radiator
Open the radiator drain tap (base of the radiator) AND the block drain tap (on the side of the cylinder block) into a clean pan. Both must be opened to drain fully. If a tap is seized, penetrating oil and patience — do not shear it off.
- 03
Flush with clean water
Close the drains, fill with clean water, run the engine to operating temperature with the heater (if fitted) on full, stop, cool, and drain again. Repeat until run-off is clean.
- 04
Mix the antifreeze
Mix a 50/50 solution of a traditional IAT (blue/green) ethylene-glycol antifreeze with clean water. 50/50 gives about -37°C protection and, crucially, the correct corrosion-inhibitor concentration.
- 05
Fill slowly and bleed air
Close both drains. Fill slowly through the radiator, letting air escape. Run the engine with the cap OFF until the top hose is warm and the level settles; top up, refit the cap.
- 06
Check for leaks, dispose of old coolant safely
Drive briefly, re-check for leaks and level when cold. Old coolant is toxic and lethal to pets and wildlife — take it to a recycling centre; never pour it down a drain or on the ground.
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This guide is a general introduction and is not a substitute for the official Workshop Manual for your car.