04 Pontiac grand prix gtp help

Several things come to mind, none of which will cost too much. That said it sounds like possibly a failed head or intake gasket, which will cost if it has to be fixed. Hopefully it doesn't come to that. You, or someone who does know how to fix a car should... First, put a thermostat in it. Modern cars are not designed to run properly without one. Make sure the cooling system is full and all the air has been bled out using the bleeder valve up by the thermostat. It's tough to get the air out of these engines. Filling it slowly with the car pointed uphill sometimes helps. Don't worry too much about using dexcool. There's probably enough already in the system to keep it from freezing. 20 degrees is not all that cold. That said, if there's only water in there and nothing else you definitely need to use some dexcool. While you're doing all this make sure your battery and ground connections are all clean and tight. That's not your problem, but it won't help if the electrical system is struggling. Once its running, rent a compression gauge and have someone who knows what they're doing check the compression on your engine. If you have the opportunity to scan it for trouble codes at the same time that will help although there's a good chance the stored codes have been lost while the electrical system was disconnected during repairs. Have the charging system tested too to eliminate the alternator as a source of the noise you are hearing although I think its unlikely that that's the problem. Good luck. Let us know how it goes. Sorry this has turned into such a bad experience for you.