I am learning as I go so I apologize if I sound like a dum dum.

The other day I looked under my hood of my 86 monte ss. Now I just had a 350 small block put in. I noticed my engine coolant in the overflow tank was below the fill line but there was engine coolant in the line because when I opened the cap it was at the brim of the line. I added coolant to the fill line in the tank. I know that when the car is running the gauge will move up it goes past the mid way mark but never gets to the red. I also noticed tonight that when I got to the show I popped the and saw the overflow tank filled almost all thecway up. I didn't see any leaks or anything unusual.as the engine cooled down the level in the overflow tank is right back at the fill line or a little higher. Is this normal. Did put to much coolant in. Like I said I am learning as I go slow be easy on me lol.

 

You could have an air lock in the coolant system. If you don't have heat it is more than likely an air bubble, but you can still get heat with an air bubble so it's not a totally accurate test. You may have to remove the rad cap and run the engine until the pump kicks in and watch the fluid drain down then fill up in the rad and repeat the process, this is how I have always done it in the past, takes a bit of time but it works.