Steve MacSween wrote: > Okay, but I always understood that unless you think the coolant has > completely leaked out, the best thing to do is to leave the car running, > open the hood, and turn on the heater as high and hot as you can and try to > lower the temps a bit before you switch off and try to put in more coolant.
I think this applies mainly when it's overheated due to excessive load or insufficient airflow -- e.g., because you pushed it too hard on a hill, or idled too long in traffic with the A/C on. If you turn the engine off, the temperature will temporarily spike even higher, so you want to keep it running, increase the airflow by shifting into park/neutral and raising the idle speed, and increase the cooling capacity by turning on the heater. Incidentally, I've noticed that my 300D Turbo seems to run coolest at about 45 mph, at least on the flat. Anyone else noticed this? I guess the curves created by the increase in cooling with increasing speed, and the increase in heat output with increasing engine load, reach a minimum somewhere around there.
