Flushing and Replacing Engine Coolant

Engine coolant maintenance is critical to the life of your engine. Automotive cooling systems are tasked with dissipating the heat generated by the engine to keep it at its most efficient operating temperature. The cooling system is designed to get the engine up to the correct operating temperature as soon as possible and to keep it at that temperature regardless of the operating conditions.

Proper temperature is important for the life of the engine. The exhaust system takes away much of the heat however parts of the engine, such as the cylinder walls, piston, and cylinder head absorb large amounts of the heat. If the engine gets too hot engine parts could expand causing engine seizure and premature wear due to a thinner oil film which could result in a ruined engine. The opposite, an engine running at too low a temperature, is inefficient, results in dirty oil, deposits, poor fuel mileage, and increased exhaust emissions.

Your typical water-cooled engine consists of: a 50/50 mix of antifreeze coolant and water, a thermostat used to bring it up to operating temperature, a water pump to circulate the coolant between the engine block passages and the radiator, radiator cap, cooling fan, hoses, the heater core, and an expansion (overflow) tank. The engine coolant plays a critical role in preventing overheating, and keeping corrosion and sediment from damaging the metal, plastic, and rubber parts that make up the cooling system.

Refer to your owner's manual for coolant change frequency. Typically every two-three years unless your car is equipped with a lifetime coolant.

Parts / Tools needed:

  • Coolant type recommended by your owner's manual
  • Distilled water (makes coolant more stable and less corrosive)
  • Coolant funnel
  • Coolant drain pan
  • Drive socket set
  • Drive-on ramps, or floor-jack and jack stands
  • Owners manual

Note: Skip steps 9, 11, 13, and 14 if your engine does not have a bleed value.

1. Visual inspection – Drive your car to obtain normal operating temperature. Turn off your engine and check for coolant leaks. Check your hoses for any cracks. Squeeze the radiator connector hoses. If they are stiff they will need replacement. Wait until your vehicle cools down before removing the radiator cap and checking for signs of wear and corrosion. Inspect the fan.

2. Raise and support the car using proper safety precautions.

3. Remove under-engine splash shields as applicable.

4. Remove the radiator cap and engine block drain plug and drain into a coolant drain pan.

5. Remove radiator drain plug and drain into the coolant drain pan.

6. Install drain plugs and fill with distilled water (for system flush). Run engine to normal operating temperature with heater set to high.

7. Drain the distilled water (steps 4 & 5)

8. Install drain plugs

9. Remove bleed valve / plug (typically located near top of radiator if your car has one). This helps to evacuate the air from the radiator as you are adding the new coolant.

10. Add fresh coolant to 1/2 of the system capacity and use distilled water for the rest.

11. Replace bleed valve loosely.

12. Start your engine and let it run to operating temperature with the heater on. Add additional water as needed to bring the level up to capacity.

13. Check the bleed valve to see if all the air is out of the system. Tighten the bleed valve if you see a small amount of fluid escaping from the bleed valve.

14. Replace the radiator cap.

15. Fill the overflow tank to the proper level for a warm engine as indicated on the tank.

16. Old coolant disposal – Check with you local recycling / hazardous waste collection service.

Serving your engine coolant along with all other required maintenance will prevent corrosion damage to your cooling system and keep your engine running at the proper temperature. Before starting on any do it yourself project be sure to consult your owner's manual for the proper parts and fluids needed.