1. Park your Highlander on level ground and turn off the engine. Allow the engine to cool down completely.
2. Open the hood of your Highlander.
3. Locate the coolant reservoir. It is located on the passenger side of the engine bay, near the firewall. The coolant reservoir is a translucent plastic tank with a black cap.
4. Remove the cap from the coolant reservoir. Be careful not to spill any coolant.
5. Add coolant to the reservoir until the level reaches the "FULL" mark. The coolant level should be between the "FULL" and "LOW" marks on the reservoir.
6. Replace the cap on the coolant reservoir.
7. Close the hood of your Highlander.
Your coolant level should now be correct.
