The BMW Z3 convertible was a wildly popular sports car over its production run, until it was eventually replaced by the Z4. Now that the Z3 is a used vehicle, it’s also beginning to age, which means that its components ageing, as well. The rear window on the convertible top in particular takes a lot of abuse over time, and can become yellowed, scratched and can even crack. Installing a new rear window on a Z3 is relatively involved, but it's possible to perform the installation yourself.
Lower the driver’s and passenger’s side windows. Open the convertible top, as though you were going to lower it. Lift it up 1 or 2 inches from the windshield frame and leave it in this position.
Run the plastic tool, which comes with the new window, between the edge of the window and the black rubber seal on the top. Do this from the outside of the car. This will break the double-sided tape that seals the window to the top. The rubber bead will be destroyed, but the new window will come with a new rubber bead.
Remove the rubber bead from around the window once it has been cut, and discard it. Locate the metal clip at the bottom centre of the window. Start by prying up the teeth on the clip with a screwdriver. Remove the support plate for the clip. From inside the car, loosen the clip. Move back to the outside of the car and pull off the clip.
Remove the old window by unzipping it from the top. Clean the top where the window was installed with rubbing alcohol to remove the old glue.
Zip the new rear window into place with the help of an assistant, ensuring that the window does not become scratched. Have the assistant hold the window in place while you start zipping it from the outside. Make sure you start the zipper on the blue side of the double-sided tape that is on the new window.
Install the metal clip at the bottom centre of the window that prevents the zipper from becoming undone. Install the clip on the outside of the window, and then move to the inside. Install the metal support plate and then bend the teeth on the metal clip down to fasten it in place.
Place an extra length of 100mm double-sided tap over the clip to ensure that it stays in place. Carefully apply a thin layer of cement to the cloth top, where it fastens to the window’s double-sided tape.
Remove the protective plastic on the sticky side of the double-sided tape. Using the plastic tool that came with the top, push the rubber bead on the window onto the tape around the perimeter of the window. Push the cloth top onto the tape with your finger around the window. Leave the top in the up position for 24 hours before putting it down again.