coolant loss
 

I have a 05 6.0 with 90,000 miles. I have been loosing coolant to the point where my de gas bottle is empty. Truck does not get hot and I my oil looks clean. I have had the pressure test done and my mechanic said it holds 16 psi. I have not noticed coolant on the ground. Where do I go from here. I am loosing a gal every month or so. I am new to the forum and new to power strokes as well but I love my 6.0.I should mention I have an SCT programmer, stock exaust (due to warranty), and cold air intake. I use synthetic oil.(rotella t-6) and ford gold coolant. Have also changed fuel filters since I have purchased the truck with 85000 miles. My egr looked dry as well

Coolant filter?
My 04 leaks after the filter it has a 'T' connected and leaks like hell from it. It drips onto the valve cover and steams so there is no evidence of the leak, I just happen to catch it one afternoon.

When you say the level of the coolant bottle is empty, what exactly to you mean?
Is it really empty, or is it just at the bottom mark on the coolant bottle?

Do you re-fill the coolant bottle to the high fill mark, whenever you see it low?
If so, you are causing the coolant loss by over-filling the bottle.
If you re-fill it with water, each time it gets low, next time you warm up and then turn off the truck, you will spill a mixture of coolant and water out on the ground (this happens about 10 to 20 minutes after turning off the engine because the coolant gets a little hotter after you turn off the motor). This will eventually lead to a lowered percentage coolant, which will cause the problem to get worse and worse, because it will overheat more as the percentage coolant goes down.
The mark on the coolant bottle is misleading (wrong).
The coolant level is supposed to stay around the bottom mark on the bottle, when cool.
If you fill it to the top mark, when the engine is cold, the coolant will expand when the engine warms up and push coolant out the cap, regardless of whether the cap is good.