As with all cars, the battery on a MkIV GTI requires periodic replacement. Over time, automotive batteries lose the ability to hold a charge. The battery on a GTI is located in the front driver side corner of the engine compartment, built into a battery box. Replacement of the battery on a GTI can be accomplished with basic hand tools, though care must be taken when handling the battery due to the presence of highly caustic acid within it.
Park your GTI on level ground and open the front hood. Use a 10 millimeter socket to remove the negative (black) terminal, followed by the positive (red) terminal.
Dismantle the battery box. The battery box is a plastic box that surrounds the battery to help protect it from the elements. The top of the box is held in place with clips that you can remove by hand, though a small flathead screwdriver may prove useful.
Remove the front panel of the battery box using a Phillips screwdriver to remove the four retaining screws. Pull the side and front panels up and set them aside.
Locate the battery retaining bolt. The GTI battery is held in place within the box by a plate located on the front of the battery which is secured by a 13 millimeter bolt. Use a ratchet and a 13 millimeter socket to remove the bolt, then remove the metal plate.
Remove the old battery. It will be heavy and delicate, so take great care. Prior to removal inspect the battery to make sure it is not leaking or damaged. If it is damaged, use gloves to protect your hands.
Insert a new battery into the location. Tie down the new battery with the retaining plate and bolt, reinsert the battery box panels and re-connect the terminals. Spray a touch of dielectric grease on the terminals to protect them from corrosion.
