Following a recent trackday I found the original ford one can give you a false reading as I lost coolant from the top rad hose after pre tightening jubilees before venturing out on track (must have just overtightened it). After pitting, sorting the leak and topping up coolant I went back out and had no probs.

I came back in and the car took 30 mins to cool down and for the fans to stop running. I then realised that I never bled the system (didn't think I'd lost much water) turns out I lost about 2 litres.

So I want to fit another temp gauge to give me the heads up that something isn't correct.

Where's the best place to retro fit an additional water temp sensor?

 

I have a boss welded on the thermostat housing with a capillary gauge in the dash

 

I drilled and tapped the thermostat housing