I was away from my office for a long time. I found many comments in my topics and I will answer your some questions. <P>My truck was made in Japan and imported to Peru.<P>I am not he original owner of the truck but I bought it three months ago and am fixing it little by little. <P>Before, I usually pour destilated water or from the river. But now I am educated and the next time when it is necessary, I will fill the radiator with refrigerant/coolant only and no water.<P>About the opening temperature of thermostat is 80 Centigrated. I haven't changed it and it is original from manufacturer.<P>About the DarrylH's comment on the intercooler fan, I haven't tought it but I will check it in the next time when I bring the car to the shop.<P>I also agree that by using potent dust flushing in the radiador may harm the water tubes in the engine block and the car shop has not done in such way but by cleaning with rads.<P>The engine warmup from bottom to the horizontal level (normal) of my truck takes 4 minutes with the engine iddling at 2,000 rpm. Is that the engine warmup long or short time?<P>Some off road fans from here told me that it is common to see some trucks diesel get overheated engine when perform a long climbing sand dunes. They advised me to try to manage to get lower RPM as possible in order to avoid the use of turbo which is the main cause of engine overheating. The turbo is only good for power to run faster in a short trail but very bad for working hard on a climbing (the par on diesel engines drops in steady line after the 2,000 rpm line) and the maximum par for the truck is around 2,000 rpm. By climbing on sand at 2,000 rpm., I am sure it won't overheat the engine for a very long slopes.<P>Rodolfo