There are two coolant hoses going to and from the turbo but I don't believe either is routed on top of the right head( it's dark or I'd run out to check). The quickest and easiest thing to do is have the coolant system pressure checked. It's like a pump with a radiator-type cap that pops on the radiator. Most garages have them. Then you just pump it up and wait and look around VERY closely for any small pin hole leaks. Also, if the car has over 60,000 miles on the original hoses, they need to be replaced ASAP, and not just the radiator and heater hoses, ALL of them. It could be other things, but like I said, this is the first thing I'd do.
As far as the humming noise goes, find a place with a lift and get it up and get the wheels spinning. If the sound is still there, you know it's not the tires. A good tech could usually pin point if it's a wheel bearing, CV joint( not likely in the rear), or something else. Hope this helps some.