MJ_Z28

This has been happenening ever since i bought the car a year ago. I stumbled upon Shoebox's coolant temp illustrations (http://csce.uark.edu/~jgbertr/rb/temp_gauges1.jpg). As i understand, those images represent the normal operating temperatures while crusing. My car runs a little shy of 210 at 55mph plus. When my car is sitting in traffic, the temps will rise to just over the 235 mark, the go down to just over 210 then back up, and down...etc,
Just recently, I have been getting low coolant light. Seems like it only comes on when the temps reach 235+, right before the temp drops. I have coolant in the reservoir and also in the radiator.
So I guess I really have 2 problems...I don't know if the 2 are related...but I'm really concerned with the high temps...it seems like my car's performance is degraded when she's that hot.
Any advice is appreciated.

Thanks,
-mj

shoebox

In the morning when the engine is cool, remove the radiator cap and see if the coolant level is to the top. If not, fill it to the top. Fill the remote reservoir to the proper cold level as well.

Your car should probably not get over 200 during extended cruising, unless it is really hot out. Also check the front of the radiator for obstructions like plastic bags or the morning news.

Harpoon Flyby

You could have air in the system or the thermostat could be bad. Two things to check.

HF

MJ_Z28

Thanks for the feedback. I checked the level in the radiator and the reservoir and everything is fine there. No obstructions on the radiator and I bled the system correctly. It there any way to test the thermostat?
One other thing I forgot to mention was that a few months ago when I went to change the coolant fluid...it was black. So we rinsed the system 5-6 times till the water was running clear on the way out. Once we did that, the low coolant light started acting up. Car has always run warm though.
I have a theory about the Low Coolant light: when the car starts sucking in coolant, I'm not sure the reservoir is feeding in the extra coolant the system needs to stay full. Unfortunatly I would have no idea how to diagnose this.
Anything more I can check? What are your normal operating temps cruising/traffic?
Thanks,
-mj