I have been reading a lot of the "stuck glow plug" posts, and one of them had an idea that made some sense to me. He recommended that you bring your engine up to operating temperature, and then take a canister of air "the type sold in camera and computer stores", turn it upside down, and depress the contents onto the stuck glow plug. His theory is that the exiting canister propellant will bring down the temperature of the glow plug, thereby causing it to contract. For about $4.00 a can, it is worth a shot. Good luck!!