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How to Change Coolant in a Car?

Published in Car Maintenance 4 mins read

Changing your car's coolant is a relatively straightforward maintenance task that can prevent overheating and corrosion. Here's a step-by-step guide:

1. Preparation is Key

  • Safety First: Allow the engine to cool completely before starting. Hot coolant can cause severe burns. Wear safety glasses and gloves.

  • Gather Supplies: You'll need:

    • New coolant (check your owner's manual for the correct type - very important!)
    • A large drain pan
    • A wrench or pliers (for the radiator drain valve)
    • A funnel
    • Distilled water (for flushing, if needed)
    • Shop towels or rags
  • Vehicle Positioning: Park your car on a level surface.

2. Draining the Old Coolant

  • Locate the Drain Valve: This is usually at the bottom of the radiator. Consult your vehicle's repair manual if you can't find it.
  • Position the Drain Pan: Place the drain pan directly beneath the drain valve to catch the old coolant.
  • Open the Drain Valve: Carefully open the drain valve (usually a petcock). You might need a wrench or pliers. Loosen the radiator cap slightly to help the coolant drain faster, but don't remove it completely while draining, as this can cause uncontrolled splattering.
  • Allow Complete Drainage: Let the coolant drain completely. This can take 15-30 minutes.

3. Flushing the System (Optional but Recommended)

Flushing helps remove any remaining contaminants and deposits.

  • Close the Drain Valve: Once the coolant has drained, close the drain valve securely.
  • Fill with Distilled Water: Fill the radiator with distilled water.
  • Run the Engine: Start the engine and let it run for about 10-15 minutes, or until it reaches operating temperature. Turn on the heater to its highest setting. Monitor the temperature gauge and shut off the engine if it starts to overheat.
  • Allow to Cool: Let the engine cool down completely.
  • Drain Again: Repeat steps from section 2 to drain the distilled water. You might repeat this flushing process 2-3 times until the drained water appears relatively clean.

4. Adding New Coolant

  • Close the Drain Valve (Again!): Ensure the drain valve is securely closed.
  • Mix Coolant (If Necessary): Some coolants are pre-mixed (50/50). Others are concentrated and need to be mixed with distilled water. Follow the instructions on the coolant container precisely. Using the wrong ratio can significantly reduce the coolant's effectiveness. Typically, a 50/50 mix is used, but refer to your vehicle's owner's manual for the recommended ratio for your climate.
  • Fill the Radiator: Using a funnel, slowly pour the coolant mixture into the radiator until it's full.
  • Fill the Overflow Tank: Fill the coolant overflow tank to the "full" or "max" line.

5. Bleeding the System (Removing Air Pockets)

Air pockets can prevent proper cooling.

  • Start the Engine: Start the engine and let it run with the radiator cap off.
  • Monitor the Coolant Level: As the engine warms up, air bubbles will escape, and the coolant level might drop. Add more coolant mixture as needed to keep the radiator full.
  • Bleeder Valves (If Equipped): Some vehicles have bleeder valves on the engine. Open these valves (usually with a screwdriver or wrench) until coolant starts to flow out, then close them. This helps release trapped air. Consult your vehicle's repair manual for the location of bleeder valves (if any).
  • Replace Radiator Cap: Once you no longer see air bubbles escaping and the coolant level is stable, carefully replace the radiator cap.

6. Checking for Leaks

  • Run the Engine: Let the engine run for a while and monitor the temperature gauge.
  • Inspect for Leaks: Carefully inspect the radiator, hoses, drain valve, and any other coolant-related components for leaks.
  • Monitor Coolant Level: Check the coolant level in the overflow tank over the next few days and add more coolant as needed.

Important Considerations:

  • Coolant Type: Using the wrong type of coolant can damage your engine. Always refer to your vehicle's owner's manual. Common types include: IAT (Inorganic Additive Technology), OAT (Organic Additive Technology), HOAT (Hybrid Organic Additive Technology), and P-OAT (Phosphated Organic Additive Technology).
  • Disposal: Dispose of used coolant properly. It is toxic to humans and animals. Many auto parts stores and recycling centers will accept used coolant. Never pour it down a drain or into the ground.