I have had a 2005 6.0 powerstroke for the past year. When I bought it the oasis report only showed 1 injector replaced in 75k. I installed the SCT tuner and all was well until we were towing a trailer one day and it threw out coolant. Ford diagnosed head gaskets and had the heads redone and reinstalled with new bolts and a new egr valve. Since the repair, the truck runs fine with the exception of a couple of complaints. Every once in a while especially when towing in cruise the truck will approach a hill and kickdown the auto trans blow a huge cloud of black smoke and take off well past where the cruise is set. In addition, after towing something, it will be very hard to start-I may have to crank for 20-30 seconds before it will start. After reading this forum, I took it into the local dealer and said it acted like the snap to connect coupler may be the problem. I stopped by several hours later and they said no codes had shown and if it was the snap to connect fitting the truck would not run at all. Anyone else experience this type of issue and how have you resolved it. I have 12k warranty left on the 6.0, after my experience should I sent it packing and go for a gas motor or ??????.
My dealer says that I should go to a F150 because of the tainted and questionable history of the 6 litre. I love my superduty diesel but I don,t want huge,out of warranty motor issues either.

 

You can have a leak in the high pressure system since they had your truck apart. I would have the dealer test the system.

 

A leak doesnt mean that it cant start. the oil (15w40) is thick when cooled so a minor leak mostly wont cause a issue untill the oil thins like your having...but like maxim said you have a leak for sure take it back again tell them it is still acting up. tell them you want to have the HPOS tested for leaks and dont pay the 100 dollar fee again... Dont give up on the 6.0 Overall it is a good motor Good luck.