Before.. This looked like a good safe spot to put the sensor. I removed the thermostat to be able to vacuum out the metal shavings, as well as to make sure there was room back there for the sensor.
I bought a 1/8” NPT tap and the proper drill to go with it. Here’s the hole tapped. I had to run the tap in a little bit, try the sensor, run it in some more, try again. Etc etc, until the sensor fit properly. NPT is a tapered thread, and if you run the tap all the way in, the hole is way too large. Found that out when tapping an intake for a IAT sensor a couple years ago. Oops!
And here is the sensor installed. Guess I’ll be taping up the harness again to add this wire to it. Ooops.