Put one in my 570. Same issues at first. Believe it was some air trapped in heater and or lines. it still takes a while to make heat but when it finally warms up its good until it fully cools down. I filled the lines and heater core with coolant first per the instructions and still had to put a " flush tee" in one of the heater lines to help bleed all the air out. I also unbolted the heater so it could lay down and be lower than my tee.im pretty sure I jacked up the front so the radiator inlet was a bit higher on my last try. Good luck! Took me a couple try's to get all the air out.