I find that the most definitive way to do it is to put some kind of thermometer in under the edge of the upper hose where it goes onto the thermostat housing. Now, slide a piece of card board in front of the radiator and run the car at about 1500-2000 RPM. Monitor the engine temp and you should hear the fan clutch engage and start to "roar" somewhere between 210-220. When it starts roaring and really moving air, then yank the cardboard out and watch the temp drop on the thermometer. If you get no air movement out of it by the time you hit 220, get the card board out of there and let it cool down. As far as a thermometer goes, I use a Fluke 88 with a thermocouple that is nothing more than a piece of platinum plated wire but man it works great.


Mark