Car Overheating / Low Coolant Light

Well, I have been experiencing this particular issue with my car for a little while now. And no one can figure out why it's acting like this. SMH.

I recently had a brand new thermostat installed in my car, along with a brand new radiator. I wasn't able to drive my car soon after because someone rear ended me and I was left out of a car for a month. I drove it for a few days and I noticed it was running a little hot. Not extremely hot, but a little hotter than normal. Then, one day, it COMPLETELY overheated. It's done this about 3 times since I had those parts installed. The "low coolant" indicator light would come out and sometimes it'd go off. And sometimes it won't. I fill up the radiator with coolant and water, depending on what type of coolant I buy (concentrate or pre-diluted) and I still experience the same issues. It's not a head gasket. We ruled that out.

Someone told me it MIGHT be a faulty thermostat and it's causing a lack of coolant to reach the engine. Which would make sense. But doesn't explain the low coolant. I have no idea what to do about this and it's getting on my last nerves, LOL. Any suggestions?

Side note:
Sometimes the needle fluctuates, depending on where and how I'm driving. Most of the time, it's at 210.

Well the most obvious idea would be to check for leaks in the common areas, like the coolant elbows, thermostat housing, etc. look for anywhere that's wet. How many miles does the car have and have you ever had the lower intake manifold gasket changed. What is probably happening is you are losing coolant and getting an air bubble under the thermostat and it is not allowing it to open... very common problem. Fix the leak, add coolant, bleed the system(through the bleeder on t-stat housing), top off coolant, and problem solved... hopefully.

What year/model/engine?

Assmuning it's not able to be found becasue it's internal or something odd:

A 3.8 NA from 97-03 could have a pin hole leak in the UIM at the EGR port causing coolant to mist through the motor w/o showing any real signs. It's more likely that it's causing a bigger issue though and sooner or later you'd hydrolock.

A 3.1 motor ...don't get me started, very possible.

A radiator cap not holding pressure/malfunctioning can let coolant out and not allow it back in.

Losing coolant also, trying to pinpoint the exact location as we speak...Thanks for the tips guys.

Found a small hole in the radiator, right below the top hose inlet.

The orginal radiator upper hose inlet was split from top down about 3". Swapped radiators out and all is nearly well. A couple of minor issues with transmission cooler lines.