My DII 2002 with 83,000 mi leak radiator fluid overnight. I added some water to the resivour (sp) and my wife ran to the store. No visable leakage after the drive. Checked the hoses, the top were hot to the touch, the bottom was warm, but not hot. Their seems to be a white plastic housing tee that connects the lower and upper hoses- is that the t stat. The trucks temp runs in normal range- no visable leakage from radiator hoses. Could it be a pinhole leak in the radiator?

 

Do a pressure test on it.

 

X2, it could be leaking anywhere, do a pressure test.

 

autozone has a pressure test kit they loan out...but they did not have the adapter for my bwm.