Initial startup cooling system troubles

Check trans fluid and oil for water. Personally when I fill an empty cooling system I pull thermostat and fill up to it thru thermostat opening. Install stat and housing with hose then finish filling the radiator. This lets air out of system. Also if it’s warm invest in a thermo gun. I’ve got a harbor freight one. The factory gauge can be misleading. Don’t rely on it or oil pressure factory gauges.