Establish a base-line, and change all hoses including heater hoses, esp. the one from the rear engine-block to the firewall (adjacent to the oil filter).
Change thermostat and use new seals & gaskets. Change the hose between the waterpump & the engine-block. If you purchase the actual factory hose and use a lot of vaseline/silicon, you can change it without doing the waterpump but it is hard!
If you can afford it, change the waterpump.
Reseda Radiator has rebuilt radiators w/warranty and re-inforced necks for $125/exchanged (http://www.resedaradiator.com
). I have one in the 1988 wagon and 1993 500E.
Check your viscous fan-clutch, if not working, either replace OR go to an electric fan.
Inspect the serpentine-belt, change out with a Goodyear Gatorback belt (NAPA has them). Check all bearings that use the serpentine-belt. If you haven't had your alternator rebuilt/replaced in over 100K miles, have it rebuilt with new bearings and brushes. Cost me $65.
Check powersteering and self-levelling suspension hoses for leaks. Replace any that are questionnable, much easier with radiator removed.
Clean the condenser out, lots of junk. The fins are easiely bent so be careful if using a high-pressure washer.
If you're coolant recovery tank is dirty, clean it or replace it. Replace the cap and keep the old one as a spare.
If you have any brown oil in the coolant use the MB oil-remover and flush 3x. Then do a MB citric-acid flush, flush 3x.
If you don't get lots of freezing weather/temps, fill up with 60% distilled water; 40% MB anti-freeze (I don't think the ORANGE stuff has a neutral PH); and 1 bottle of RedLine Water-Wetter.
After doing this, and with a 1995 C36 AMG M104 engine, my engine temps never get past 100 even when climbing the desert-hills to Las Vegas at 105-F going 75 MPH.
1988 360TE AMG