Ford F-350

I have a 2006 Ford F-350 Super-Duty 6.0 Liter Diesel, with less than 28,000 miles om it. Two weeks ago I when started the engine white smoke was comming out of the tail pipe, proportionly with the RPMs of the engine. I had to drive four miles to my house all gauges said all was ok. I checked the oil and coolent levels, the oil was ok and the coolent was a little low. I filled coolent and re started the engine and there was no smoke. A week latter it did the same thing, this time the check engine light came on, I took it to the Ford Shop I was told it was the EGR valve. They changed it, but it is still smokes once in a while and lossing coolent somewere other than a leak that I can find. Could this be a head gasket or a turbo going bad?
April 14, 2007.

Open the radiator cap and start the engine. Rev the engine and look for bubbles coming from the radiator. Bubbles indicate exhaust gas getting into the coolant. There are also kits that have dyes that change color when exhaust gas is present.

Apr 14, 2007.
That truck has to be still under warranty? Take it to the dealer, tell them you want a leakdown test done, will confirm a headgasket leak, or not.

Apr 14, 2007.