PeachParts Mercedes-Benz Forum - View Single Post - 606 engine temperatures: What constitutes “normal”?

RunningTooHot · #1 04-23-2004, 10:55 AM

I inadvertently hijacked another thread, (http://www.peachparts.com/shopforum/showthread.php?threadid=92407) so I felt it appropriate to start a proper one so that people searching the archives can find the suitable information.

My question is what other owners of 606-engined cars are experiencing as far as running temperatures during warm & hot weather. The reason for my question is that my particular car (a 1995 E300D, 124 chassis) runs hot in comparison to my 123 300D (I know, I know, apples to oranges.)

Specifically, it runs at ~85 degrees under normal, low load & low ambient temperature conditions. It will go up to about 90-95 going up a hill, but that doesn’t concern me that much. However, when it is warmer outside (80-90 degrees), the car runs between 95 to 102 at high freeway speeds, and I’ve seen as much as 105-107 when puttering around at slower speeds. (AC use doesn’t seem to affect it very much – although the electric fan is actuated with the freon pressurization or temp rise, well before the coolant thermo switch kicks the fan into high speed.) I’m a little afraid of what will happen later this summer…

The car has a relatively new radiator, and I cleaned out the fins on the condenser & radiator when I first got the car. I replaced the thermostat when I did a flush (exact same results). The thermo clutch *seems* to be working properly, and the temperature sender is not to blame, its accuracy verified with an infrared thermometer.

One way to get the temperature down a bit when in “city driving” mode is to keep it in a lower gear & have the engine spin a little faster, thus pumping more water through the engine. (I recognize that it also increases the fan speed & pulls more air through as well) However, it seems as though there is plenty of relatively ‘cooled’ water in the radiator, but there isn’t enough water flow from the pump. (I’ve checked upper vs. lower hose temperatures when the car is really hot, and the lower hose is considerably cooler.)

Either this is ‘normal’ behavior for a 606 engine, or perhaps… I have a strange theory. I am wondering if maybe the water pump vanes have deteriorated due to cavitation, and therefore it isn’t pumping the amount of water per design specs. I also recall reading something somewhere about plastic impellers on a Mercedes engine, but I don’t recall which one (a search returned nothing). Either that, or the engineers cut it *really* close on the specified pumping volumes, trying to avoid parasitic losses & increasing the mileage a bit. What do you guys think???

Thanks Again!
RTH