Many times it starts off with a mis-fire and a glow plug needs to be changed. When trying to remove the old glow plug it BREAKS! A nightmare for sure. Our broken glow plug removal tool is actually designed for the Mercedes Sprinter engines, however skilled technicians that can improvise a little have been known to use our B900-0199 on Duramax engines without removing the head. While there are no guarantees, it's definitely worth trying instead of removing the cylinder head. If done properly the threads won't be damaged. We have Glow Plug Thread Repair kits in case things don't go exactly as planned. Need help with application? Give us a call at 800-734-8665 x251.