This is an update to the below original post I made earlier today:

I just drove the car, and the coolant light came on when I got back. Tank is muddy/redish/brownsih looking, I have to open to check level. Can I add normal Preston pre-mix stuff to hold me over until Monday/Tuesday. Does color of tank mean rust/air in system? The car has been to dealer 3-4 times since May for cooling related issues. They replaced coolant when they did Head Gasket in May, and had to have at least added coolant two weeks ago when they did the Thermostat. Even if the problem I mention below is in fact within normal temp ranges, you'd think they'd at least mention the fact that the tank is showing signs of bad things, if that be the case. I'll have to speak to them on Monday. I've spent @$$loads of money on what seems to have no results, save for the head gasket, that was of course leaking.

Original Post:
I have a '93 300E, 3.2 I6, late '92 build, only 70k miles on it.

Temp
For the last few years, the car runs hot in slow or stop and go traffic, especially on hot days. The temp needle stays around 80-85 on the highway, but then reaches up to 110-ish when in slower traffic, especially after coming off the highway into slower local traffic, red lights, etc. The aux fans and engine fan all work. I tried to turn the engine fan with engine off, and it turns as much as I want to turn it, all the way around. Old posts here say that would mean it is going bad, not spinning at full speed, but M-B mechanics and other service people say that it is normal, that it should turn when off (that being the purpose of having a "clutch", not fixed to engine). Did the turn-fan-by-hand test only apply to earlier models? Or are the dealer techs wrong? Dealer did the head gasket early this summer, and problem seems to have become worse since then, but that may just be the summer heat. Had the thermostat replaced a couple of weeks ago, little to no improvement in temp. No leaks found.

Idle
The car sometimes has a slightly "bobbing" fluctuating idle speed when sitting still in park or in D.

Tranny
Clunks into gear from park or R. Sometimes when I make a special effort to pause and wait a second or two when shifting from reverse to drive, I get a short slip and a clunk before car jumps forward. After that, when driving, car holds gear long before upshifting when cold. Hard, heavy acceleration pulls up to redline, shifts smooth and crisp.

Thanks for any help or advice anyone can provide!!!