Reasons:
* Safety: A hot engine can cause burns from the hot coolant and/or the hot radiator cap.
* Accuracy: Coolant expands when heated, so adding antifreeze to a hot engine will result in an inaccurate reading of the coolant level.
* Potential for damage: Adding cold antifreeze to a hot engine can cause thermal shock and damage to the engine.
Procedure:
1. Let the engine cool completely. This may take several hours depending on the ambient temperature.
2. Locate the radiator cap. It's typically on the top of the radiator, but may be on the coolant reservoir.
3. Remove the cap carefully. Be sure the engine is cool before removing the cap.
4. Add antifreeze. Check your owner's manual for the recommended type and concentration of antifreeze for your vehicle. Add antifreeze until the coolant level is at the "full" mark on the reservoir.
5. Replace the cap. Tighten it securely but avoid overtightening.
6. Check for leaks. After a few minutes, check for any leaks around the radiator cap or hoses.
Note: If you are not comfortable working with antifreeze, it's always best to have a qualified mechanic perform the task.
