Inuchiyo,
First thing to look at in an overheating problem, is your cooling system.
does your cooling system have a silicate (white residue) build up when you look down into the radiator (a COOL radiator) through the filler tube? Are you using a "Green" coolant or a "Red" one?
The problem with "Green" coolants is that they already have a "Silicate" content when they are manufactured. When this combines with a "Hard" water being added to make up the 50/50 mix in the system, Silicates really build up.
Green coolants also are continously putting down a coating of silicates (by their very nature) to protect the cooling system from corrosion. THis build up does not conduct heat away from the engine components to the coolant worth beans!
Use an Extended Life Coolant (Red) such as the one recommended by Caterpillar International. I have a lot of experience in Heavy Fleet operations in the Deserts of the American Southwest and the swamps of Florida. The right coolant, and the upkeep of that coolant (VERY IMPORTANT) can make or break an operation. Texaco Extended Life Coolant (ELC) could solve your problem. In Eurasia Texaco is called CALTEX. Go to this site
http://www.chevrontexacolubricants.com/worldwide/asiapacific/default.asp
Click your language, then click the extended life coolants. Check with your local Lube Engineers (in Eurasia) on this one. They should be of great help with your friends situation.Hope this helps