My '91 350SD runs a bit warm (some would call it HOT!) here in the Las Vegas summer heat - with daily ambient temps of well over 100F - especially in stop-&-go traffic. Out on the freeway it stays around 90C/100C, but in city traffic it will sometimes get pretty high on the gauge, probably around 115C - especially after a LONG day of driving all over town.

I just had the radiator flushed and refilled, but they used the green stuff (after I specifically asked for Zerex G-05, darnit!). I drove the car again today and the temperature only went slightly over 100C, but it has been up to 115C before. When I picked it up from the mechanic, I let it idle in the parking lot for about 20 minutes - maybe that's where the heat built up???

I'm looking for advice on where to start my search for the problem - I'm not opposed to a complete cooling system overhaul, but naturally I'd like to avoid the expense unless it is determined to be ultimately necessary!

I've already corresponded with several of you about my problem, and many thanks for all your help!