The New Beetle’s rear quarter glass fixed window is held in place with a special urethane formulated for high bond strength. Typically this type of adhesive has a 1200 PSI tensile and 550 PSI shear strength. This basically means it’s virtually impossible to pull the window away from the frame with the adhesive intact, and difficult — but possible — to cut through it.
Specialty tools, like a sheath blade for a reciprocating saw can be used, but these are generally for heavy use auto body and salvage yard applications.
For only two windows, a good wide blade with a handle and a heat gun can handle the job.
Using a sharp blade, cut out the rubber window seal that surrounds the quarter glass. Pull out as much as possible to expose the urethane bond between the glass and the rubber seal.
Sharpen the wide blade tool so it will move through the sealant more easily; also get a length of 1/2″ L-angle bar (aluminum is fine) and a long strip of scrap metal to help pry out the window.
Starting at the bottom of the B pillar edge, apply a heat gun to the glass and, at the same time, press in the wide blade. As the sealant softens, the blade will begin to move through it.
After about a minute of heat, you should be able to completely insert the blade through the sealant so that it appears on the other side of the B pillar.
Because the sealant is hot, it will tend to re-adhere so insert a small wedge or screwdriver to keep the gap open. As you move up the B pillar edge with the wide blade, continue to insert small wedges to keep the gap wide enough to prevent re-attachment.
Next, work along the roof edge with a long piece of scrap metal while spot heating the glass along the edge (sharpen the metal at its leading edge if possible).
When you have progressed about half way across the glass top, use the same technique on the bottom of the glass with a 1/2″ L-angle bar.
Apply heat while pushing the L-angle bar in along the bottom edge. You may need to gently tap the bar with a rubber mallet.
At the half way point, move to the inside and insert the wide blade tool starting at the top. Apply heat and push to the end of the window. At this point you should be able to carefully pull the glass top an inch or so away from the frame with the bottom acting like a hinge. Insert a sharp blade and cut the exposed bottom rubber seal from the inside. The glass can then be slowly pulled away from the frame.
The safety glass in the quarter window is designed to shatter into a million pieces under stress, beginning with an spider-like cracking that happens instantly. If the glass cracks but doesn’t shatter, don’t lose hope — the situation can be mitigated.
Using protective gloves, immediately tape the glass on the inside and outside. Packing, duct, or painters tape all work fine. From the inside, carefully push the window out. It should detach basically in one piece, leaving a “crust” of glass fragments along the window edge. Use a sharp knife to clean up the edge.