What does Ford Tech look for...blown head gasket

[Hivolts]

My trucks in for loosing coolant and fuel mileage. What are the sure signs a Ford Technician looks for when determining if the head gasket is blown? Right now they "think" its just a bad egr valve....but I don't want them to think...only 33 days left on my warranty. Is there a sure sign...white smoke? diesel in the antifreeze? oil in the antifreeze? etc. Lots of posts on this but nothing for certain.

[jimmyz32]

[m-chan68]

Cooling system pressure well in excess of 16 psi, venting out of degas bottle under load.

[Hivolts]

Thanks for the help. My truck is in the shop. I find out tomorrow. Is there a special tool that you attach to the degas bottle to check pressure? It builds a lot of pressure and blows out like a regular radiator and it's been spitting some fluid out of the degas bottle.