Cooling System Assistance Options

[brandon702bmx]

I'm on here a lot lately... seems like I am becoming a nuisance more than anything.

To be fair, I've "researched" other sources to see if I can answer my question properly but none of them really seem to answer it.

Anyhow, I removed the radiator because my car was in an accident. (had to do some repairs to front end) I installed it and filled with coolant...

I've been driving the car recently and noticed that when I come to a stop, the car is leaving puddles of coolant + overheating at some times. At other times... it takes a while to get up to operating temperature. The gauge stays well below the half way mark. I'm talking about 1/4 of the gauge even while driving it for periods of time. I also forgot to mention, it fluctuates as well. It seems like it wants to go to operating temp and then goes right back down.

My research has brought me to this conclusion:
When filling radiator with coolant, jack the front of the car so that it is elevated.
Leave the radiator cap off, place a funnel in the hole and make sure it fits snug, fill to where the coolant is visible at the lowest point of the funnel.
Turn the dial to the hottest setting and put the heater on low.
Allow the car to run, reaching operating temp.
Squeeze rad hoses to assist with removing air.
Add coolant as needed until fluctuating coolant levels stop as its replacing coolant with the air in the system.
Screw cap rad cap on.

Everythings good after that? I'm sure to most this may be common sense but I was unsure of doing this.

Also a speculation since sometimes the car won't reach operating temp, the thermostat is bad and isn't allowing proper circulation since it may be getting stuck?
What should be troubleshooted first?

[Box]

If it's the connector of the sensor that's the issue then that's easy enough, just get a new sensor. If it's the wiring harness connector then you'll have to find one either from someone online that cut it off or get it off a car in the junkyard or being parted out. For what it's worth there are two sensors, one to the ECU and one to the gauge. So it's not the end of the world and the original is just a dummy gauge anyway, might consider going to a good aftermarket coolant temp gauge so you actually know what the temp is and get the information in real time. I know why they do it, but why performance oriented cars especially have dummy gauges or an in-comprehensive gauge setup in general is beyond me.