What size are the bolts for changing a thermostat on 96 Chevy blazer?

The bolts holding the thermostat housing on a 1996 Chevy Blazer are typically 7/16" (11mm). However, it's always best to double-check with a socket set to be sure before attempting the repair. You might find a slightly different size depending on the specific engine (4.3L, etc.) and any previous repairs. Having the right size will prevent stripping the bolt heads.