the other thing pulling the thermostat can do is cause the coolant to circulate too quickly, so that the rad doesn't get a chance to do its job - the coolant leaves the rad before it has a chance to exchange the heat. this can lead to overheating.
let's think about this for a second. i'm no metallurgist, but I think the notion of trying to prevent head cracking by upgrading the cooling system does not necessarily have merit. At most, the coolant circulating through the engine is going to hit maybe 250F. If you're in boil-over situation, it'll be higher than that, with some steam. Temps like this are nothing for cast iron. what causes cracking is either extreme temp fluctuations or variations, or fatigue over time due to heating and cooling of the metal (expansion and contraction). it could be that these trucks, now 15 years old, are starting to see some fatigue set in, and cracks are developing. it could also be that there's a design flaw in the head itself that doesn't allow enough coolant pressure in the head, so there are cavities, perhaps localized steam. since air and steam to not absorb heat, you get extreme temps in some parts of the head that are not being cooled, while other parts are being cooled as normal, so there's a temp differential that causes stress and cracking.
so, it seems to me that the important thing is to make sure your coolant is fresh, and that your rad cap holds pressure, to prevent steam and cavitation. beyond that, a larger rad or fixed fan might not help the situation as much as we think it would.
the last thing, of course, is to drive it like you ought to drive a 5000lb truck with a 97 hp engine. it's slow. that's all there is to it. I've taken trips out to the mountains into a howling headwind...the needie sits at 80kph until i hit the shelter of the mountains. egts sit at 1000F the whole time. if you're in a hurry, forget it. that little engine is pushing a big ole brick into the wind.
i don't know what's going on with these 2L-TEs, but it's crazy out there. oh well, looks like i'll have a decent selection of parts rigs for the forseeable future!
