Chrysler Repair: Overheat and loud metalic noise on starting, gear teeth, slow traffic

Question
My car-Chrylser LeBaron convvertible 3.0, 6 cylinder with overdrive has overheated in slow traffic-I took out the thermostat and it was fine.  I then replaced the theromstat with 192 degree stat. I did not replace the coolant sensor.It has overheated again in slow traffic. The fan seems to kicks in when the temp gets above the half way mark. I let my car set and for the second, after several days of setting idle-then on start-up there is this loud noise(like shaking a bunch of ball bearing in a metal pan. It is awful-loud and scary-but it only lasts a few minutes. What is going on..is that an indication of a bad water pump or a bad timing belt or both? I had begun noticed this noise sometime ago-a short/brief incident after setting for days and then on start up-- prior to any problem with overheating. There is certainly something going on.....What are your thoughts.

Answer
Hi Marianne,
I would first, while I'm thinking about it, suggest that you might put in a lower temp thermostat if one is available for the engine, say around 180-185 to give yourself some extra room for hot days. The fan coming on shows that the temp sensor is working ok, but it would come on sooner in the warm up situation with the lower temp thermostat. I can't think of anything relative to the temp experience that would cause a loud clanking noise at start up. But one idea related to the starter motor is that the Bendix gear on the starter motor is sticking in the out position such that it is meshing slightly with the teeth on the flex plate and continues to do so until it slips back into the resting position. That clanking of gear teeth on a thin, large diameter metal plate would produce the sound you describe, but it would start as soon as the engine started and your release the key to the normal position for running. If the engine sound didn't start immediately after using the starter motor but rather was delayed for even a few seconds then this would not be a plausible explantion.
The repair would be to remove the starter and have that Bendix unit replaced, or maybe if it hasn't ever been replaced then just rebuild/replace with a refurbished unit the starter motor.
If the temp hasn't gone off scale with a release of steam from the overflow bottle I doubt that any of history you describe would be causing a cooling system issue. Water pumps I don't believe will make that loud a noise, though there is a bladded impeller inside that could be rubbing. However I would think that it would have leaked coolant if it got that bad. If the timing belt has gone 100,000 miles or more than replacing it would be a reasonable preventive maintenance and that would be the perfect time to also replace the water pump. But if that is not case, then I would want more solid proof that it is the water pump that is making the noise. The engine is of non-interference design so if the belt breaks or slips it will not cause internal engine damage. Just a shut down of the engine.
So if the sound is immediate, do look into the starter motor Bendix unit being the problem. Please let me know what you learn or have any other questions.
Roland