Yesterday I tried to fix something that didn't need fixing. I thought the thermostat bolts where too short. So I tried 1 longer bolt for the 9 o'clock hole and I torqued it a little too much and I felt it give way. Anyway I got a different 10mm bolt 1.0 thread pitch same as OEM and it grabbed on because it doesn't have the nipple at the end with no thread so it goes a little deeper, I'm thinking I should just leave it since it grabbed on and doesn't leak at all.

Anyway. Is it safe to drill and tap to use 12mm bolts? Maybe 11mm though very rare? Like I said I have no problem now but I do want to make it as good as it was before.

 

If anyone is interested a 7mm-1.0x30mm bolt will fix this with a 7mm-1.0 metric tap bit. 7mm is better than 6mm anyway. Works with a 11mm socket, rare and it's often not included in a socket set.

I got all of this from Home Depot. The tap and die set is made in the US.