There are spot welded nuts or tabs that the bolts thread into. Since you have a 14mm (or 9/16") head someone tried to force an oversized bolt in there and broke the weld. Your only option now is to cut or grind off the bolt head. After you get it apart you can use a riv-nut tool to make the repair. 

http://www.aimfasteners.com/about_rivnut.html#.U6Ja0Y0g-00

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Marc Perdue
Sent: Wednesday, June 18, 2014 7:32 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Front bumper removal conundrum

Hi all,

I didn't get any suggestions on removing my front bumper, so I'm asking again, separately from the other questions, so here it is:

The two bolts on the rear bumper and one of them on the front, are 13mm bolts and came off easily. The second bolt on the front bumper is a 14mm bolt and won't come off at all. It feels like there was a welded nut inside the bumper that has come loose and there doesn't seem to be any way to get to it to remove the bumper, or tighten it back up for that matter.

So, this time I'll ask some more specific questions:
1) Do you all know if there are welded on nuts inside the part of the body to which the front bumper attaches?
2) If so, and if the welds break and the nut turns free, do you know of a way to get to it to hold it still and remove the bolt?
3) If all this can be done, how would you put it back together?

Thanks,
Marc Perdue