My 6.2 has had only 7 out of 8 glow plugs since 2003...one up front on the passenger side unscrews and will come out about 3/8",but wont come any further--I have tried every thing I have read online and thought of myself to get it out without busting it off,but to no avail..
Vise grips,I pried on them with a bar,even stuck the glow plug in my electric drill chuck and ran it in reverse while I pulled outwards on it..for a good 5 minutes,with zero success..its dead too,so its not like I can plug the wire back on and say "good enough,leave it".
I have not tried the official 100 dollar "glow plug remover" tools offered by OTC and various other online sources,and wont,unless someone had one I could borrow..
My bet is the dam thing will bust off regardless of whatever tool or method is tried,the thing is probably expanded to gigantic proportions or bent at a 90 degree angle or something..my injector lines will likely break off if I tried removing them and the injector too,so I just assume leave it alone..
Every year about this time it needs a few new glow plugs,and I give it another go,try to get that one out--about 2 weeks ago I decided to unscrew it after a 25 mile ride and try removing it again..hoping being hot it might finally come out..
--no luck --I even tried starting it up with the glow plug unscrewed and floored it 4-5 times and it only puffed compression out on the first stroke,then ran normally like it was still screwed in!.
I was not brave enough to drive it around that way,but chances are it was not going to blow out intact like I hoped it would..also feared it might break and do damage to the cylinder and piston..
It has already had one glow plug in the #3 cylinder decide to shatter while I was driving it a few years ago,and it sounded horrible!..
I limped it home 3 miles clattering,then when I was close enough to home to walk to it, I floored it several times in first gear till it hit the govenor--at that point I cared not if it blew up.(and kind of wished it would)....and it quieted down,I guess the chunks blew out the exhaust,but I wouldn't be surprised if it wounded the piston or cylinder some...
I think a push rod may have got slightly bent,it has a loud lifter noise after a cold start for a few minutes since that happened..
Glow plugs just plain suck on 6.2's,and most diesels period...they should have made them as big as spark plugs,not with puny 3/8 hex heads that rot away quickly and tiny 10mm threads...
I have had more rust away than fail electrically ,I had to replace them while they were still able to be removed,the hex was whittled away to a nub on several of them..they still glowed fine ,but if I left them in much longer it would be hell to get them out..