Is my '93 90CSQ running a little warm?

[Kelvin]

Diana Johnson groused...

>The temperature gauge needle used to sit at about 1/4 of the
>scale and even on a hot day would sit a little below half way.  The
>gauge needle on this car is usually exactly 1/2 way up the scale unless
>I'm driving on the freeway, and it's only 40 outside.  It started to
>overheat about a week ago, so we took apart the coolant reservoir and
>found a crack.  After replacing it with a new one and tightening the
>hoses, I really thought it would run cooler.  Am I being paranoid or
>should I be nervous about summer?
My '92 100CSQ runs hot if I'm stalled in traffic. At will even boil over 
in temperatures as low as freezing. Above 37 degrees F, I'm fine, 
however, in that I can turn on the airconditioner. The radiator fans run 
continuously then and bring the temperature down to the normal operating 
range. At highway speeds I'm fine, but in stop-and-go or gridlock, I have 
to watch it. I've also replaced both temperature sensors (yes, there are 
two), the fan relays, and the thermostat (twice) but with no noticeable 
difference. So the cause still mystifies me and my mechanic. It's done 
this since the car arrived at about 90,000 miles and it now has 127,000 
and going strong.

Kelvin Kean