Ok, so here goes nothing......

Drove to work the other morning , went through town fine, got on a straight away, and bam, overheated, steam pulled over turned off the ignition and popped the hood... coolant everywhere... hot hot hot.... the gauge was in the red....Got towed home grabbed the 07 tahoe and went to work....
p.s. been 25ish both days when overheating

Came home put water in it, started it up, RUNS FINE.... tried to recreate the problem or find any leaks... NO SUCH LUCK, refilled everything with antifreeze, tried burping the system filled the overflow tank ....... Runs fine drove it to work a few days.... Checked the Radiator, and its low, probably 2 to 3 cups low..... overflow is where it should be....

No Milky Oil, No Milky Coolant, Steams out the tailpipe for a little while in the morning(just like every other car) and stops after a minute or so....
NO LOSS of power runs just fine.....

Today I got on the freeway and the temp gauge started creeping.... Got close to the red, pulled off started going slow and it crept back down.....Got to the office popped the hood, and coolant was in the overflow, but not in the radiator..... topped it off before coming home, and got home, low again.... ITS GOING SOMEWHERE IN A HURRY and i cant find out where.....

Bought a new Thermostat, gonna put it in this weekend, checked the fan cluth, seems to be pretty whimpy, wont lock up when i let it go at normal temp.9but shouldnt even be running when on the freeway at normal temps.... I CAN SEE NOOOOOOOOOO coolant loss, and it doesnt appear to really be coming out of the tailpipe
Bubbles going in the overflow tank from radiotor but seems normal since theres no water in the top of the radiator to go into the overflow tank..

this set of heads and headgaskets, with new headbolts only has about 4k on them. Im baffled..... help someone!! by the way, these are rebuilt heads from another 3.0 from a headshop.....
HELP HELP HELP

 

Replace the thermostat.

 

either a sticky t-stat, or the coolant may have been freezing in some spots if there wasn't a proper mix. at 25 degrees however i would bet the t-stat.

 

Mine does this all the time due to a known leak draining away all my coolant (slowly). Been too lazy and it's too cold outside to mess with it right now. In my case when the coolant level drops to a specific level (about 3 qts low) the temp gage will climb into the red and the ventilation system blows ice cold. If you have similar symptoms, you may have a leak you don't know about.

If there are no leaks, another possibility is a bad water pump or belt. Had this happen to one of the Bobcats at work, it kept overheating but coolant levels were just fine. Once I saw that things that were supposed to be turning weren't, the solution became obvious; the belt had broken and the water pump no longer working as a result.

 

I've seen this under two circumstances:

1) I had a 3.0 that had a failing water pump due to a timing belt that was too tight. The tight belt wore the pump bearings and it would intermittenly lock up the water pump and overheat. Start it two hours later and it would be fine.

2) You've got a blown HG that's venting into the combustion chamber. No milk in the oil, no other real indications other than some mist on start up and a radiator that's missing water after a few miles. A leak down test will catch it OR make sure you're not dropping water under normal driving conditions.

 

lol, this isnt the good news i wanted to hear........