My 1990 240 with 225k has been overheating while sitting in traffic in hot weather. It will usually creep up to just under the red block on the guage. Turn on the heat, temp guage goes back to 9:00.

No problems on interstate or even city driving. but on really hot days, the temp guage goes up if i'm sitting at a traffic light for more than 30 seconds or so.

me and a buddy drained and flushed the radiator. took out the old thermostat and found it broken!! Like in two pieces! that was strange because the car always seemed to warm up ok, and by feeling the upper hose it felt like plenty of hot air was getting through. Anyway put in a new thermostat just like that one and the car still overheats like before.

before every screams fan clutch, the fan seems to have plenty of resistance when i spin it hot and cold. and i can hear/see it click into high gear when i let it idle for 5 minutes or so. also i don't seem to be leaking coolant, which would be a sign of a bad water pump, right? all the belts seem ok but maybe ya'll know of something to look for...

any chance it could be a timing problem? i've also heard people say its possible i got a bad thermostat from autozone...(?)

help...i know i'm killing my engine here by letting it get that hot on an almost daily basis. sadly, i don't really have the money for a real deal mechanic.
thanks in advance