Originally Posted by wingman358
The cheapest, fastest, probably longest-lasting way would be to drill and tap a larger thread in the holes. If you really want to reuse the same bolts, you could try to size a Heli-coil or other threaded insert (see Threaded insert - Wikipedia, the free encyclopedia
) but I'm not sure if you'll be able to find the right size/thread pitch to reuse the stock bolts in the Heli-coil... good luck and keep us updated.
I did not mention Heli-coils or other threaded inserts because of what the material it goes into. Here being white/aluminum casting (ie intake manifold). I have seen inserts break alum castings, pop out (as in Spark plug heli coils) and next removal of the bolt, take the insert right out because of insert bonding with the bolt used to hold said part. I agree in this case as it is only a thermostat, it may hold, but for reasons I just mentioned may cause problems in the future.
Many temp repairs are just that, temporary. It becomes a judgement call on time/money/life expectancy. I myself grew up with the moto "Do it right the first time, so I don't have to pay for it twice".
Good luck, and Be Safe.