The other night while I was sitting at a stoplight the coolant temp was three tick marks over the middle mark on the coolant gauge. It usually NEVER goes over one tick mark over the middle. I started driving and it went down probably because it is 5*F outside. I left the car running while it was parked and it went three marks over again and the fan never kicked on like it usually does. I waited until the next morning and the coolant level was at the hot mark while it was cold. So I'm low on coolant and now overheating. I tried to take the cap off the overflow tank and the bottom of the cap is still in the tank while the top one was off. I searched for it and it is common. But I cannot take it off for the life of me. It will not unscrew or pry off for anything. Would it be a good idea to just get a new tank? Any of you ever have a seized coolant cap.