In my endeavors to change my glow plugs I have had a set back. 3 of my 6 came out with little effort, and 3 are stuck and the bolt has been sheared off. I let the plugs soak for about 30 min. with PB Blaster before I even tried to unscrew them, and that seems to have not helped at all.

Any ideas how to get the 3 stuck plugs out? The stuck plugs are 1,3, & 4 front to back.

Thanks,