How To Flush Cooling System Of A Car

The engine cooling system plays a crucial role in preventing your car from overheating. Also, it helps to maintain the optimum temperature in all conditions. However, the efficacy of the coolant mixture wears out over time from scaling and rusting. A contaminated coolant system may put your car at risk of a sudden breakdown. To prevent coolant system failure, it is important to know how to flush cooling system. You simply need the right tools and follow some steps to do this.

Some Precautions For A Cooling System Flush

All the required things to drain a coolant system and to add the new coolant mixture must be ready before we get on with how to flush cooling system.

You will need a disposable pan or container to collect the used coolant as it drains out. Make sure the liquid is disposed of safely outside the reach of children or pet animals. Ask around, especially in the local auto-parts store, to find recycling options for the used liquid.


For the fresh engine coolant mixture, you will need distilled water and the correct coolant or antifreeze for your car (check your owner’s manual to know). You can also add anti-rust sealer and protector in the mixture.

A chemical flush product can be used in the mixture if you are keen on doing it in a more efficient way.

Keep a screwdriver or wrench (depending on the drain plug). Always use a pair of gloves to avoid skin irritation from contact with the chemicals.

Never remove the coolant reservoir cap from a running or hot engine, as the pressurized area poses the risk of hot fluid shooting out. Let the system cool down before you loosen any plugs or caps.

How To Drain Coolant System

Place the disposable container for collection underneath the car and use screwdriver/wrench to loosen the coolant drain plug. Then remove it and drain the coolant off.

After safely disposing of the used coolant, put the drain plug tightly back.

How To Flush Cooling System

Fill up the empty reservoir with water until it is full. Start the engine and pour more as the water gets pumped in, allowing you to fill up the system completely so there is no air in it. Then, add the entire bottle of the chemical flush while the engine is still running, or simply use distilled water only.

how to flush engine coolant
Flushing a cooling system. (Photo Source: nearsay)

Then, follow these steps for how to flush engine coolant:

  1. Put the reservoir cap back and take the car on a short 10 to 15 minutes ride. If the engine seems to overheat, stop the car immediately.
  2. After the drive, allow time to cool down the engine before emptying the cooling system by unplugging the drain.
  3. As the water drains out, remove the reservoir cap too so there is no water stuck from the suction at the top part. Turn the engine on for a few seconds after the water is drained off to force out any remaining water from the coolant system.
  4. Turn the engine off and tightly put the drain plug back in.
  5. Fill up the coolant system with the appropriate type and volume of coolant as provided on your owner’s manual. Pour the coolant into the system. If it starts spilling, start the engine and keep adding as the liquid gets sucked in.
  6. Add the anti-rust solution (if you want to add one) before you pour your last gallon of the coolant mixture.

Finally, place the reservoir cap tightly. Take the car for a final ride to run the brand new engine coolant through the system. And, this is how to do a coolant flush.