Possibly air trapped in the CoolantSystem.
Park vehicle with front end elevated on ramps\jacks or a curb by a few inches; set the EBrake.
With engine off & cold, remove radiator cap, start engine, let it idle & warm up.
As engine warms up, ThermoStat should begin to open & allow flow into\thru the radiator;
when you see coolant begin to rise out of the cap opening, shutdown engine & reinstall cap.
Allow engine to cool for an hour+, then top off radiator with coolant as needed.
May need to do this 2 or 3 times to completely bleed all air from CoolantSystem.