My 2015 cadenza is overheating at high rpm’s, i will over heat driving over 50 mph i got ther tstat replaced and I’m still having this issues. I don’t see any leaks. Also when going up long hills the temp increases slightly, can someone please help? I can literally drive all day around town or under 50 mph so i don’t think head gasket but im not sure, bringing into dealer tomorrow, also my shift gear locked when i tried to put it in drive today, i notice the little yellow light flickering so im thinking it maybe a fuse, i will check to see if my brake lights come on. Im so over this car tbh