Yes, I used a nice clean brick as the flat surface to help "shape" the grill into being flat with a mallet. Hey, it was free and worked and I'm not going for concours here so yeah. I did.

I'll try some more penetrating oil and holding the end of the bolt.

 

It's a carriage bolt. The underside of the head is square, and fits into a square hole in the bumper. Put your hand (wearing a work glove) on the head of the bolt and zap the nut with an air wrench, it'll zip right off

.

 

Either an impact to spin it fast or a die grinder or torch to cut it off. Once that round head starts spinning, you're screwed.

 

never heard of someone using a brick, but hey, it worked. awesome.

i'd probably just take a die grinder or angle grinder to the bolt head. once carriage bolts start spinning they can be really, really hard to get out of there.

 

If the bolt has already been damaged to the point that it rotates freely, just tack weld the bolt to the bumper and remove the nut. After all, the bumper is trash.

 

Yes, yes...I love all the responses..but everything I do with my own tools and on a limited budget. I don't have any air compressors or welding machines yet