For a while now Ive heard a bubbling sound inside the cabin after I shut off the rodeo. It sounds like its coming from where the heater core is.

Does anyone else notice this or have any idea what causes it?

it sounds like
1) you have air in your coolant system and the air bubble is stuck at the heater core
2) you have a leak in the heater core.

fully burp the system, try it with the nose on an incline and then try it the other way around.
feel the carpeting, especially in the passenger side, especially near the top and on the hump. that's where the leaking heater core usually first shows up.

//bc