How to Replace a Cabin Air Filter in a BMW 3 Series

1. Purchase the correct replacement filter. BMW uses a charcoal activated filter for its 3 Series. You may be able to purchase an aftermarket substitute at an automotive parts store, but you can purchase a factory replacement at your BMW dealer.
2. Shut the engine off and pull the hood release. Locate the cabin air filter cover in the rear part of the engine compartment, right beneath the windshield (it extends to the width of the engine bay).
3. Twist the three fasteners counterclockwise to unhook the cabin air filter cover. Once the fasteners are loosened, pull the entire cover up and set to the side.
4. Pull the old filter out of the compartment. It's clearly visible with the cover removed. Inspect the compartment for foreign items and debris; remove them, if applicable.
5. Insert the replacement filter into the compartment. Position the cabin air filter cover back in place and turn the three fasteners clockwise to secure it.