Refill with proper mix coolant (not water) and replace the thermostat and get a new radiator (overflow tank) cap -- the cap has failed and isn't holding pressure. This allows the coolant to boil, overheating the engine.

Do not run without a thermostat in a Benz engine, the coolant will not circulate through the radiator without the bypass passage closed by the flap on the back.

Use only Whaler or Behr OEM thermostats from a good indpendent mechanic or the dealer, do not buy on at the local parts place -- the "clones" usually don't seal (and in fact often will not physically fit in place!).

If you still have overheating problems, look for a leak at the water pump at the bottom weep hole -- might only be a trickle. Also check the AC drain off the transmission for coolant from a leaking heater core. Last, make sure the "cold" side of the radiator gets hot when the engine is warm -- if not, the core is plugged and it's new radiator time.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!