I have a 99 f250 with the triton v10. I have been having very minor coolant leaks and it would smoke a bit when started but quickly clear up. I ran a diagnostic on it and found #6 cyl to be misfiring. Upon removal of the spark plug after sitting I notice coolant on the plug. A leak down on the cyl showed air escaping to the degas bottle. So my question is anyone have experience with these? What I am trying to figure out is what is most common on these, head gasket, cracked head or cracked block. I recently aquired the truck so I have no idea of the history of overheating on it. I assume at some point it must have gotten hot enough to cause this, but really can't be certain.

 

The most common point of failure for a coolant leak is a cracked intake manifold.

Did you perform a leak-down test on all all cylinders, or just #6?

 

If you're getting pressure leaking into the coolant reservoir, that's definitely a head/head-gasket leak. Could be a cracked block, but we won't go there

Sounds like it's time to pull that head and see what's up.