Car usually runs 185-190, last week temp. jumped up 20-25 degrees, seemed odd even though temperatures here in Reno are in the low to mid 90’s. Every thing under the hood looked fine, decided to check t-stat, and found this!
I have seen that take place. It's due to failure of that folded over sheet steel cradle that supports the rod. The sharp edge of the round hole was the starting point of a crack that lead to the full failure of the cradle. You should be using a Robert Shaw type thermostat if you never want to go thru that again.
