Water Temperature Gauge Installation Tips-Range Rover
I confirmed yesterday that the coolant overtemp switch is indeed a Metric thread M15 by xx (xx is some number that I forgot). I was able to find an adapter that converted the metric thread to a NPT but still using a T to incorporate the coolant switch AND the temp gauge bulb is too difficult. There simply isn't enough room for a 1/2" NPT T in that area. I'll drill and tap the head when the engine is out for a rebuild job. In the meantime, I was able to remove the radiator brass plug (cap?) and replace it with the autometer temp gauge bulb. Now that was a precise fit. At least I'll have some sort of a temporary temp indication!
Using a tee for pressure sensors is not a bad idea, but I do not believe it is recommended for temperature sensors. On shipboard systems I work on the temperature sensors are required to be a certain depth into the flow steam.
Try a good hydraulic shop for adapters. I had to do something similar for my oil pressure switch. The fitting for my gauge was 1/8" NPT, and it took two adapters to get it to fit where the OEM oil pressure fitting was.
Aftermarket Gauge Install Info:
Fitting for Top Radiator Hose (thanks Tony Brooks)