1. Park your vehicle on a level surface and turn off the engine.
Allow the engine to cool down for several minutes before opening the coolant reservoir.
2. Open the hood.
Locate the coolant reservoir, which is a plastic tank with a black cap that is usually mounted on the driver's side of the engine compartment.
3. Remove the coolant reservoir cap.
Be careful not to spill any coolant.
4. Check the coolant level.
The coolant level should be between the "MIN" and "MAX" marks on the coolant reservoir.
5. Add coolant if necessary.
If the coolant level is low, add a 50/50 mixture of antifreeze and water until the level reaches the "MAX" mark.
6. Replace the coolant reservoir cap.
Tighten the cap securely to prevent leaks.
7. Close the hood.
_Note:_
_Be sure to use the correct type of coolant for your VW Golf GTI, as specified in the owner's manual. Also, be careful not to overfill the coolant reservoir, as this can cause the engine to overheat._
