I have a 2004 Chevrolet 2500 with the 6.0. Starting last summer, it began randomly overheating. I could check the coolant and be good, go out for a while, and all of the sudden it would be overheating, and the coolant would be empty. Let it cool down and then fill it back up and it would be fine, sometimes for months. It hasn't acted up since September but now it's doing it again. Today it happened to me twice in a day. I filled it back up the first time, about two hours later it happened again. What could be causing it to basically dump coolant like that? Theres no slow leak that I can see, it just dumps everything and overheats? I can stop and sometimes there will be coolant running off everywhere after it's done this. Fill it back up and it doesn't do it again, like I said, sometimes for months. I have noticed that it seems to be more likely with the AC running, which I don't run much, but this afternoon it wasn't on.

 

i had the same problem with mine and now overheats all the time going uphill. I took the thermostat off (and when I looked at the radiator the radiator is so tiny) and still overheats. My next move is to replace the clutch fan with a "flex-a-lite 294 " electric dual fan and hope will work for me

 

I had the same issue here in Florida. What I ended up doing was replace the water pump. There is a small weep hole on the bottom and what was happening that it was leaking so slow it was evaporating on the block before it would cause a puddle or show any sign of leaking. I also replace the Tstat at the same time and fan clutch and havn't had a problem since.