4.7s are notorious for slight head gasket leaks. we see this almost daily at my shop, and your symptoms are classic combustion leak. you may even be able to smell a slight whiff of exhaust in the coolant...
I wasn't able to smell it. The leak was tiny, but the chemical tester sure recognized exhaust fumes in the coolant. I pulled all the plugs and scoped each cylinder. I found out that number 5 cylinder had coolant in it. At first I used a UV light and saw the coolant glowing in that cylinder, then I stuck the scope down in and took this crappy pic. Not a high quality image, but you can see the green coolant pooled from about the center, going diagonally to the right corner of the pic.
To be absolutely sure I was seeing coolant, I rocked the truck back and forth...the movement was enough to see the liquid shaking back and forth in the cylinder.
Anyway, I'm glad that I didn't have to pull the head off. I'm pretty impressed with the 4.7L. This thing is running excellent for having 271K. I drive it daily and it doesn't burn a drop of oil and the coolant stays up to the neck now.
