Q: Water gauge showing red hot, but engine is not hot.....is it a sensor if so which one?

I changed my knock sensor plug because it was worn out. As I turned on the Supra to check if the engine light came off, I noticed that the water temp gauge was red hot, but that couldn't be possible because the engine was no where near hot. So I decided to change the thermo stat and the gauge continued to display red hot. Water pump is good, radiator is good, thermal stat is good, and I just changed thermal sensor about 6 months ago. My best guess is that at the time I changed the knock sensor plug, I might have bother a cable, but the knock sensor is no where near thermal state nor thermal sensor. If anyone knows the cable I might have bother please let me know. I'll be changing the thermal sensor and I hope that fixes it. Other that, anything else I can change please let me know. My supra is a 1986.5 3.0 Liters 6v

Thanks alot