Hello DarrylH, according to my experience, when I lost the cap when it droped into the engine and I was not able to find it and gave it up. So I taped it with a cloth. Then I went very soft, trying not surpase the 2,500rpm and I found the open radiator keeping the same level of water in spite of the fact I have traveled around 15 kms and the gauge of temperature was horizontal. <P>About the comments of Fasteddy, I feel that my truck will need an electric fan but let me check first my next trip to desert on January. If it is necessary, I see no space to put an additional fan. The other way is to change the trigger level of temperature to be lower so that the fan starts to work whenever the gauge of the temperature raises 5 centigrades above to the horizontal. Any ideas on how to improve the fan power or starts to work when the car goes slow on desert. <P>Rodolfo [img]images/icons/shocked.gif" border="0[/img]