Didn't think anything of it but i have noticed a few times this week when i start the truck after it's to temp, shut down for an hour, the restart i hear coolant gurgling iin the dash area??? Was very noticeable this evening. Still no overheating and heat blows nice and hot. Still getting the blows warm to a certain temp, then cold to a certain temp, then hot once to temp then will stay hot until fully cold soaked. Think my tstat is not acting right?

 

Somethings up, how are you getting to get the gurgling, what level of coolant at and is it changing level? I wonder if you have a small leak letting air in? How old is thermostat? Water pump?

 

I'd put a pressure gauge on the cooling system and see what it's running at.

I know my truck was gurgling quite a bit after starting and after shutting it off it would do it.
It turned out to be head gaskets leaking, after I put a gauge on it went up to 18 psi at a idle.
Hope it's not the same thing going on with your truck. But putting a gauge on it will tell you for sure.

 

Could be the same on mine. Saving for the hg job but just having a gut feeling it is something else. I'll have to gauge it again when i get the chance.

Ha--coolant just below new mark,new pump, and mishi tstat.
I've been thinking an air leak for over a year. Level is staying consistent (checking at cold soak) can't think of how to find the air leak.