Radiator Problem
 

My 2006 Equinox is having major radiator problems. It ran hot about three weeks ago. There was no coolant in the reservoir. I added water and it ran o.k. for about three weeks. This past Saturday the problem started again. We took it to a shop and they said the problem was with the cap which they replaced. They could find no leaks in the radiator. This morning, the same scenario occurred again. It ran hot. I checked the reservoir and it was empty.
I added water and made it to work. My father-in-law thinks that the fan is not cutting on. Can you offer any help? Thanks!

First if there are no external leaks, I'd suggest checking for anti freeze in the oil. Need more info on what you've "done."