No hissing, no drama with the cooling system at all. It just always reaches some kind of equilibrium at this spot. Anything wrong with this? What explains it? If I fill it to the actual cold mark and it settles here, the extra had to have gone somewhere.

 

Mark the tank with a Sharpie. If it stays there, you are fine. Each truck tends to settle at it's own location. Not a problem unless it keeps dropping.

 

You might be slightly over pressure for any of a number of non critical reasons, the excess could be going out the overflow pipe. Once it gets to the happy level it will be fine.

A catch bottle on the overflow would prove it out

 

I had the same situation on my old truck. Changed the cap and the issue went away.

 

Completely normal.

 

I experience the same level setting and have also been curious about this. It must be reservoir related because I have a TD5 engine in mine.

 

If @abran ever comes back out with coolant tanks, I'll take two. I regret not getting them when they were available.