Diggy923

Last year I replaced my water pump and thermostat. Before and after the installation, my heater blew/blows cold in the winter when the temperature is freezing. If I let my car warm up for 7 minutes or so, the heat would blast hot, then as soon as I get on the road, the temp guage would gradually drop all the way to the bottom on the cold mark and my heater would eventually get cold. So basically, the colder the temperature is outside, the colder my 'heat' is blowing. If it matters, in the winter time when I start the car and set the defroster on for a few minutes while I warm up the car, a strong smell of gas is in the cabin. When I set the control to anything but defrost, the gas smell goes away. Please help! Is it a faulty thermostat? Thanks in advance!