Now ya'll have got me wondering about my 300D. It is strange. The car runs/drives/starts up great, no problems whatsoever but sometimes when I drive it and let it sit for a day or so I still have pressure in the coolant reservoir which results in a slight leak at the seal for the aux water pump (I am figuring because of the elevated pressure). I am not seeing any oil in the coolant nor white smoke. I do see the slight loss of coolant because of the aux pump. Once the 240D is up and running I may pull the head just for the heck of it to see if there is anything obvious. My narrow minded way of thinking would lead me to believe that if there were a problem then the "pressurized" coolant would eventually wind up in a cylinder somewhere which would cause a whole different type of problem (bent parts). Today when I got home I opened the reservoir cap and relieved the pressure which seemed to be comparable to the amount of pressure that is there after a day or so of cooling off. Funny thing is, during this time, the radiator was hot but the water temperature in the reservoir was not even warm. Also, when I opened the cap the level in the reservoir did not move.