93 3.0 heating troubles

[morgan51]

So for the last 2 weeks my truck was only heating to about 160 degrees so I decided to put a hotter thermostat (195) since the old one was 180 degrees and NOT stuck open. After the 195 degree thermostat was put in, I started the truck to check for leaks and to ensure everything was functioning normal. I kept my eye on the temp gauge and sure enough, it ran up to 190 then fell quickly to 170 degrees then back up to 190 and so on. Anybody seen this before?

 

[Sasquatch_Ryda]

Air pockets stuck in the cooling system.

 

[morgan51]

I checked the coolant level and it was a little low. I topped it off, about a quart, and still the same problem.