Thank you so much for your folks' lightning speed respondses. I love this forum, and learned so much from everyone.
Before the pump leaked badly, the temperature gauge stopped at 85 at all time whether or not the AC was running. After the pump was replaced, engine run hot all the time, and promted me to flush the coolant after I read from the treads that MB coolant is either clear or orange in color. Wrong coolant used with the aluminum MB radiator may be the cause for the high temperature, I thought.
So, I brought the car to a euro car shop other than the local MB dealer mainly because it was quoted about half the cost. The pump cost plus labor. Sounded reasonable, but end up costed me almost twice as much by the time everything was done. My belt was streched loose due to may be the poor workmanship for fastening, or too hot in the engine compartment that cause the belt to badly stretched because wrong type of coolant used.
I will give the thermostat a shot, and thank you all for being so kind to help. I assume that the dome shape half cube which is connected to the upper hose located at the top of the water pump will be the housing of the thermostat.
Was the thermostat's characteristic changed after overheating occured? Just curious !
By the way, is there any modification in resistor change for the boosted HP just like some treads suggested? Or the 202 chassis (C280) does not have the resistor as other models that were discussed?
1994 C280, Red hot with cream interior 106K miles
2000 ML 320 Silver
1991 190E 2.3