Engine Mechanical System

Coolant Repair Procedures

16steps
~96min
4/5difficulty
Done 0 of 16

Filling and Bleeding

Never remove the radiator cap when the engine is hot. Serious scalding may be caused by hot, pressurized fluid escaping from the radiator.
When filling engine coolant, be sure to cover the relay block with a cover and do not allow coolant to contact electrical parts or paint. If coolant spills, wash it off immediately.
  1. Make sure the engine and radiator are cold to the touch.
  2. Remove the radiator cap (A).
  3. Loosen the drain plug (A) and drain the coolant.
  4. Tighten the radiator drain plug securely.
  5. After draining the engine coolant, clean the reservoir tank.
  6. Fill the radiator with water through the radiator cap and tighten the cap.
    For the most effective air bleeding, slowly fill with water and squeeze the upper/lower radiator hoses.
  7. Start the engine and let it reach normal operating temperature. Wait until the cooling fan operates several times. Increase engine speed to help purge trapped air. Stop the engine.
  8. Wait until the engine has cooled down.
  9. Repeat steps 1 through 8 until the drained water is clean.
  10. Slowly fill with a mixture of coolant and water (55~60%) (except North America, Europe and China: 45~50%) through the radiator cap. Squeeze the upper/lower radiator hoses to release air easily.
    • Use only genuine antifreeze/coolant.
    • For best corrosion protection, the coolant concentration should be maintained year-round at a minimum of 55% (except North America, Europe and China: 45%). Coolant concentrations below 55% (except North America, Europe and China: 45%) may not provide sufficient corrosion or freeze protection.
    • Coolant concentration above 60% reduces cooling efficiency and is not recommended.
    • Do not mix antifreezes/coolants of different brands.
    • Do not use additional rust inhibitors or anti-corrosion products; they may be incompatible with the coolant.
  11. Start the engine and let it run until the coolant begins to circulate. When the cooling fan operates and coolant circulates, add coolant through the radiator cap.
  12. Repeat step 11 until the cooling fan has turned on 3~5 times and sufficient air has been bled from the cooling system.
  13. Install the radiator cap and fill the coolant reservoir to the "MAX" (or "F") mark.
  14. Run the vehicle at idle until the cooling fan has cycled 2–3 times.
  15. Stop the engine and wait for the coolant to cool down.
  16. Repeat steps 10-15 until the coolant level stops dropping, bleeding air from the cooling system.
    It takes time to bleed all air from the cooling system. Add coolant when the engine is completely cool. Recheck the coolant level in the reservoir tank 2-3 days after coolant replacement.
    Coolant capacity: 6.6~6.9 L (1.74~1.82 US gal, 6.97~7.29 US qt, 5.81~6.07 Imp. qt)

Test yourself

A quick Kia Optima Hybrid Owner's Manual quiz: every answer comes with an explanation and a link to the manual page.