cskone,
I am not a mechanic, nor certified technician. As always I always encourage anyone working on/near vehicles to seek certified individuals to work on your vehicle.
Below you will find only some suggestions of what your current situation may be. I can only write about my own experiences and what I have learned from others throughout this forum.
Take a look at the link I pasted below. In a nutshell I had a similar situation. I would first check your hoses to see if you have wear/tear that would cause a leak. Many times what happens is that you won't find anything leaking under your vehicle because it would burn up within the system before reaching the ground. Another suggestion is to check your coolant overflow and see how low/full it is. It could be needing a head gasket. Does your CEL illuminate? If so, are you able to pull the codes? Most likely these are only simple precautions to get you started.
You mention that the vehicle heater is "gurgling", this may be your heater core (maybe a crack), but more than likely what I can tell from my own experience and some research is that it could possibly be a slipped cylinder sleeve(s) in the engine since you mentioned the coolent, which may be leaking into the engine and causing the beginnings of any over heat, if it hasn't already. Give your front passenger footwell area a good check, especially under your floor mats, sometimes the fluid drains around there and gets soaked up by the padding under the carpet.
Depending on how severe this could be, you may also need a valve job as well depending on how much wear/tear is on the vehicle, due to the carbon build up on the valves from the gasoline.
If you do have a slipped sleeve, I have heard of mechanics and machine shops replacing the sleeves, but its not always the correct fix. The resolution is almost always to replace or rebuild the engine. In that case, if you replace the engine, be aware of the specs. Let me know what your thoughts are after you read the below forum. Let us know.
"Ocean Wave-like" sounds, Gurgling & Sloshing
