87 535i overheating

well winter break is coming along and i decided to fix my gf`s brothers car for fun, it has been sitting for sixth months, he says it overheats and takes fifteen minutes to do so. I checked the oil and there is no coolant in it, and i dont see oil leaks around the head so i doubt it would be the head gasket. They think it is the radiator but it doesnt leak so that cant be the problem. What have you guys repaired/ do you think?
stuck thermostat? Waterpump? Head gasket? I havent looked in to the engine yet could the fan clutch not work or a dead fan? sorry for the questions i am used to my integra

Hi,
Everything you said could be the cause of your problem. There are so many overheating threads, you can do a search and find them. I would start with the fan clutch that seems to be the highest post for overheating, there is a newspaper test I keep hearing about but someone else will have to tell you exactly how to do it.
Hopefully someone can point you to the post, it is a cheap way to find out if its the fan or not
Good Luck,
PS: Ill try and find the post for you also

Yup, the number one cause of this problem is the fan clutch. If you can drive it down the highway and the temperature is fine, then it overheats while sitting still, you'll know it's a fan clutch.
Flunky
PS-I changed mine myself. Took a half hour. The hard part is holding the fan still while you put the big-ass wrench on it...