Help! How to remove boogered up hex head bolts

New car day.

Something not German. 

I am a big fan of the impact driver, especially in an easy to reach spot like yours. But you need to hit it very hard with a very large hammer. Even with a rounded hex it will probably come free. Make sure its rotating the correct way first by pushing down on a flat surface and watching it turn. Think heavy gloves, a helper and a sledgehammer. 

Appleseed said:

Got a Dremel with a cut off wheel? Carefully cut a slot with said wheel as deep as you can without dinging the plate. Use the biggest Stright blade screw driver, impact driver/ugga-dugga.

I'd try this or drilling, but heat first before trying to turn them to weaken any thread locker used when last assembled. 

In reply to bearmtnmartin (Forum Supporter) :

Any videos of this process?  I have one, but have never used it.

The hammer mechanic in me says cut a slot from 12 ro 6 o'clock right through the center of the flat surface, then use a chisel and hammer to push on the slot loosening the bolt.  Bang from the left n the bottom, from the right on the top.

Buy Nev-R-Seize.

Cutoff disk to turn it into a flathead screw, impact driver to loosen it.

Heat the bolts orange before trying to remove next time.  This expands them so they are no longer under tension, and it melts the thread locking compound that is probably there (even if just leftover from the OE bolts).

Those look countersunk to me, I don't think slotting the head is the easiest method because you're just asking to mar up the bracket. Obviously not OE so dealership sourcing new bolts is probably a nogo. Mcmaster if there isn't anything local (which would be crazy. There's really not hardware store around? Fastenal? Tacoma Screw? Heck, even Ace hardware has a pretty good selection of the metric stuff).

I'd try oversized torx with an impact first but probably end up hitting it with a good drill bit real slow with something as cutting oil since you're doing a few of them. Same as others have said, drillbit the same size or just a hair smaller as the threads so the head just pops off. Looks like m8 or m10?

In reply to iansane :

A little notch in the bracket isn't going to hurt a thing.  It only has to be strong enough to be held on by four weak-headed bolts after all.

There are already so many good suggestions here, I think it's likely you'll be able to get the bolts out whole, but if you must resort to drilling, I'm surprised nobody has brought up our good friend the left hand drill bit. My experience with them has been that after some drilling, more often than not, the bit will end up spinning the remainder of the bolt stub out.

Given how long this is taking, the number of opinions given and the number of people involved, I'm beginning to think this is a government job. Lol.

In reply to ShawnG :

I'll hold the workbench down if you can hold the creeper down.