Hey guys I'm hoping that you can help me out. My car is overheating. It's fine at idle till it gets driven then spikes to the L and above. At first I thought it was the waterpump because it was leaking. I've replaced that as well as the thermostat because I thought it was bad too. At first the coolant wasnt circulating thats why I changed out the tstat. Now it is going through. I took it for a quick spin and it doesnt seem to be down on power so I dont believe its the headgasket. No fluids appear to be leaking anywhere to me. Also when the car is on L and above I turned on the heater and it blew cold. So possibly the heater core is bad? I wouldnt think that would have anything to do with the overheating though. One last thing is I put stop leak in the radiator sometime last year and this problem started well after that. Any thoughts?