Originally Posted by amosfella

My 95 S320 has been running hot since I got it. I bought it in Nov with about 200K km on it. All winter it has been running at about 100C. By winter, I mean -20C or lower, but even on the warmer days +15C, it kept to 100C even, no fluctuations. Lately, I have been seeing the temp spiking to 105C while highway driving at 110 km/h (70 mph). And when sitting still, the Temp will almost reach 120C after it has been driven. Aux fans suck air the right way. My reading really doesn't give a good indication of what is wrong.
I hear varied opinions, from thermostats, water pumps, radiators, and fan clutches. Tomorrow, I'm going to warm the car up, and see if it's the fan clutch.
And suggestions of what and why that problem is??
Also, I have been thinking about doing a citric acid flush through the coolant system. Would I need to use distilled water, or would tap water be good enough??