Is there anything wrong with bypassing the heater core/heater control valve? I am having overheating problems even in 60 degree weather. I just flushed the coolant and filled it with the proper misture. It runs fine for about 30 mins of driving then starts creeping up... Ideas? I don't think the radiator is the problem because about a year ago i drove for like 50 miles at 70mph and it cooled fine.