1991 Chevy Caprice my temp gauge goes higher then normal

hey there i just replaced a lower rad hose cause mine blew so anyways when i dorve the car after the temp gauge once the car was warmed up it would go to the half way point but then keep climbing all the way up to the tick just before the red and just so u know before i blew the hose the temp gauge would never go past half its just weird it will go up high like i said and stay there for a few minutes then finally come back down to where it should be but ill press the gas pedal to pass someone on highway and it will go up again my anit freeze is up and whatnot im pretty sure all air bubbles in coolant r gone car blows hot air i thought it could be thermostat but i was told if its putting out heat then its fine ? thanks alot