Okay so once again my 04 svt is giving me trouble again, last night it got down to 8 or 9 degrees (pretty cold for southern tn) but the car overheated and started blowing cold air no matter what setting I put air on. The coolant reservoir was blowing hot coolant from under the the reservoir cap. Any help would be great, is it the thermostat stuck closed ? The heater core blocked and need replacing? I'm at a loss here fella's.