2001 4.0L ticking and coolant issue

[getafewlives]

Hey guys, I just picked up a 2001 eddie bauer awd 4.0L explorer today. It's the first explorer that I have bought, and I intend on using it during the winter when I take the mustang off the road.

Here's my issue though. The guy I bought it off of said it needs a new head gasket, but he is just guessing and doesn't really know. Right now the explorer drives just fine and seems to perform just as it should. Plenty of power, smooth idle etc. But when you take the rad cap off the fluid is low, but the reservoir is full. He said that he noticed a while ago that it was like that and topped up the rad, but it ended up doing the same thing again. Would this be a head gasket? If the vehicle isn't over heating or having any issues, should I worry about this right now?

Another issue, when the explorer is running, I can hear a slight ticking from the top end of the engine (pretty sure top). It's also intermittent. As I was standing there listening it would come and go away. Any ideas of what it is and how to fix it? Or if I should ignore it?

Thanks in advance!

2001 Eddie Bauer Explorer
4.0L AWD 110,000 miles

 

[getafewlives]

Oh and also, I can't get the heater to switch from the windshield defroster, any ideas of where to start looking?

 

[getafewlives]

I should also mention that the ticking increases with rpm until about 3k then it seems to go away. It is most apparent at idle.