https://www.s2ki.com/s2000/index.php...rheating-issue

 

Sorry for all the post but I was doing this on my phone. There is a link to billman's coolant bleed procedure in one of the threads. Follow that.

 

Sounds like thermostat sticking closed. You can test this by removing it and putting in a container with water and microwaving it to see if it opens... Or just replace it because it is cheap. Doing this will also allow whoever is working on the vehicle to fill, bleed, the coolant system (which air in the coolant system causes similar symptoms).