Both really, I first smelled it inside the car two days in a row while I was sitting in it while it warmed up, and the last time, I was standing outside the vehicle while it was idling. I plan on checking a few of the ideas out today, to see what I can find. I do have a coolant leak checker where you put a different cap on and pressurize the system to look for external leaks. I will probably give that a try and see what comes of it.

 

Corrosion at the hose clamps is a clue to look for, that will allow coolant to escape at hot temperature, also air in the system, and look at the weep hole in top of the water pump

 

Put it under pressure and see where it's leaking.

 

The filler neck has been known to crack and crumble.