Coolant Drain and Refill

Easy step by step instruction on how to perform a coolant flush, though appearances will differ, the process is the same on most vehicles.

Difficulty Rating: 4 of 10

Tools and Supplies Needed

  • Coolant
  • Coolant catch basin
  • Protective eyewear and gloves
Begin with the car on level ground in park with the emergency brake set. The engine should be cool before beginning to avoid pressure inside the cooling system.

Step 1 - Locate the radiator fill cap which is usually in plain sight and on either the radiator itself or on the coolant reservoir.

Locating Radiator Cap

Step 2 - After the cap has been located, remove it slowly while allowing any residual pressure to bleed off. Caution: The cooling system will hold pressure when hot so be careful when opening the radiator cap.

Releasing Residual Pressure

Step 3 - Once the radiator cap has been removed, locate the radiator drain valve. (Note: Some vehicles are not designed with a valve, in this case the lower radiator hose must be removed from the radiator to drain coolant.)

Locating Coolant Drain Valve

Step 4 - After locating the coolant drain valve, open it by turning the valve counter clockwise.

Draining Radiator Coolant

Step 5 - After the coolant has finished draining, reinstall the drain plug and tighten.

Reinstalling Radiator Drain Plug

Step 6 - Now the coolant system is ready to be refilled, always use manufacturer's recommended coolants.

Manufacturer's Coolant

Step 7 - Using a funnel, slowly pour 50%-50% coolant and water mix into the radiator or reservoir until full. Once full, start the engine and allow to warm while adding coolant mix.

Refill Coolant Reservoir or Radiator

Step 8 - Once the engine has warmed to operating temperature top off coolant to the full line or top of the radiator and install cap.

Reinstall Radiator Cap

Once complete double check the coolant level in a few days to make sure there are no leaks or that air bubbles in the system have worked themselves out, lowering the coolant level. Also check the coolant level in the reservoir.

Helpful Information

Coolant can become corrosive if left inside the system for extended periods of time without changing. To prevent this corrosion the coolant must be changed at regular intervals. In cold weather coolant or antifreeze (same thing) prevent the engine block and other components from freezing. Coolant and antifreeze refer to the same product, in below freezing, coolant lowers the freeze point hence the name anti-freeze and in warm weather coolant helps raise the boiling point, "coolant". All engine coolants are highly toxic and should be kept away from animals.

There are many types of engine coolant, colors range from green, blue, red and yellow which possess various properties that help against corrosion and overheating. Be leery of harsh chemical flushes because they can cause premature cooling systems failure. Some manufacturers recommend partially filling the system with coolant and the remained with water, to about a 70% coolant 30% water mixture.

A cooling system should be serviced within manufacturers recommendations to stay in top condition. If a normal service schedule has been neglected, coolant can change its chemical base composition to an acid which erodes vital components.

Best Practices

  • Always use manufacturers recommended or approved coolant.
  • Check system for leaks after flush is complete.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


Please use our question form if you have a specific question about your car as we are not able to give you a full answer on this page.

Article first published