I noticed while driving down to Houston today, that the temp gauge would creep up way past where it usually is, really only when idling, and only after I'd been driving for more than an hour (although that first hour was
only highway driving, not idling...).
When at ~40+mph, the needle stayed dead center, which is where it'* always been when the engine is completely warmed up/operating (200°F?). Houston traffic being what it is, I had to turn on the heater at full blast when I was idling, so the temp would remain around its normal value. Otherwise, the gauge would go up to the next marking, and even a little past it. I pulled over immediately after I first noticed that, looked at the coolant...the level is fine, it'* just above the "full-hot" line on the reservoir.
I'd noticed some mild overheating like this (but not to the same extent) before, but it would occur sometimes even at highway speeds too. It turns out that I was about a quart low on oil, oops.
So I added a quart and everything seemed to be great; temps remained dead on at the center of the gauge, needle straight up. Today was the first time I had this problem at idle though....what could be causing this? It'* even cooler than it'* been lately too...
The only thing I can think of is that the coolant looks kind of...dirty, or something. As far as I can tell it doesn't look like there are any other fluids in it, it just looks dirty. Would this overheating problem be something that a simple coolant flush would fix? (I've not done that since I bought the car in September, and I really have no idea what the interval for doing that should be...)
I should mention too that I think the "low coolant" sensor has been acting up for months...it'll trip the light in the DIC at random times, when the coolant is visibly NOT low, and then it'll go away after a minute or two. I'm assuming that'* something separate though, since it'* never been overheating at idle until today...
As always, any help is greatly appreciated.