Headgasket is toast.

If the coolant system is over-pressurizing, then the exhaust is getting into the coolant and pushing all the coolant out.
You can limp it home by taking the thermostat out.
I went through this a year or so ago.

 

Yeah, the more reading I do, the more its starting to sound like the HG is on its way out. Must be pretty mild right now though, as the coolant thing is the only symptom. I know it will get worse. I'm really torn at this point whether or not I want to dump more cash into a tired motor, or just run it into the ground, so I can justify buying a rebuilt one...

 

You can pick up a complete gasket set from engnbldr for pretty cheap.
Re-doing the headgasket can be done fairly easily over a weekend.
I suggest getting the head checked and levelled.

What was the reason for the headgasket to pop? Did you overheat it? Low oil? Low coolant? Check engine code? All of these things can blow you head gasket.
If you don't fix the issue, you won't get more than 15k km out of a new head gasket. Ask me how I know...

 

I'd have to say age is the biggest factor here. When I bought it the diffs/trans fluid was nasty, but the engine oil and coolant was pretty good. I've since flushed the crap out of everything, but you can't really wash neglect away. No overheats or engine codes, don't know a whole lot about its history. I do know that I check the fluids religiously and change them early or on the dot, but I've only owned it two years.

 

Run it until it blows. Then do a 3.4 swap. Cheaper in the long run, more power, better reliability and better gas mileage. You could end up spending $1500 for head work only to have a rod let loose

 

HG should not be a difficult thing for any good mechanic to diagnose. Go out and get a block test kit, link in previous post. Go ahead and get a leak down test done if you would like that will also be a good indicator of engine condition. 3.0 are known for HG issues but, don't condem the gasket until you have done a basic diagnostic prodedure. Also be aware another common although some times inconsitant coolant leak on the 3.0 it the water tube under the lower intake plenum, between the heads.
Good luck on the hunt

 

Additionaly if you determine it is nessasary to change out your headgasket be sure to check, or have checked, both the head and the deck of the block to insure they are flat. If you get your head machined be sure to use the correct thickness gasket afterwords as cam timing will be affected by the relation of the head to the block.