I have a 1999 C230K with 200,000 km (120,000 miles). It has the 2.3 litre supercharged 4 cylinder M111 engine. Runs well with great fuel economy. This winter, in recent cold temperatures (-5 C or about 23-25 F) the car does not warm up to full operating temp of 90C - more like 70C to 80C. The air from the heater is warm enough but not really hot. When the car is idling the heater air cools noticeably and then warms as revs increase. Is this normal? This doesn't happen with our other vehicles so I don't know if this is normal for this model or the pump/thermostat needs attention. Also, the car has a difficult time keeping the side windows clear of condensation. I don't see any fluid loss at the water pump or loss in the amount of coolant. Are these signs of a worn water pump or faulty thermostat? Anything else I should check? Thanks, Paul

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1989 300E
1999 C230 Kompressor
2003 Toyota Sienna (aka family van)

Also owned:
1964 Chevrolet Impala (first car)
1972 Fiat 124 Sport Spider (first sports car)
1976 VW Scirocco (first new car)
1970 Pontiac Parisienne (epitome of bland)
1980 VW Scirocco (last new car)
1953 GMC 6x6 (amazingly well engineered)
1967 Austin Healey 3000
1987 F150 4x4
1978 F150
1987 VW Jetta
1992 Toyota Previa
1949 John Deere Model M

Step one: Check coolant level and mixture. If that checks out proceed to step two.

Step two: Replace thermostat.

If the pump were going out you'd most likely be seeing overheating and/or leakage from the pump.

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Anyone who thinks a 300D is fast drives too slow.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 351,xxx miles
08 Triumph Street Triple 21,xxx miles, lowered 10mm in front, Pirelli Angel GT tires, otherwise stock.

X2.

Out of curiosity, what antifreeze are you using in those frigid temps?

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'89 260e (212K Mi.), '92 400e (208K Mi.), '92 400e (not a misprint) (146K Mi.), '95 C220, '81 240D--Sold

X3 Tstat

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Thank you. Dealer has the thermostat (and very competitively priced). Will also flush cooling system as the existing coolant (Mercedes coolant) is 3 years old.

Thanks for your help!

Paul

__________________
1989 300E
1999 C230 Kompressor
2003 Toyota Sienna (aka family van)

Also owned:
1964 Chevrolet Impala (first car)
1972 Fiat 124 Sport Spider (first sports car)
1976 VW Scirocco (first new car)
1970 Pontiac Parisienne (epitome of bland)
1980 VW Scirocco (last new car)
1953 GMC 6x6 (amazingly well engineered)
1967 Austin Healey 3000
1987 F150 4x4
1978 F150
1987 VW Jetta
1992 Toyota Previa
1949 John Deere Model M