92 Z24 Overheating

Can someone help...I was coming home from work, It was -30c outside and I had no heat at all coming out of my heater but as soon as I got home my car over heated.......just the past summer I put a new heater core and thermostat in it...but if anyone can help please!

Im going to guess since its a 92, you have a 3.1. I would check your gaskets. either your head gasket or you intake gasket.look under your oil cap or pull your PCV valve and see if there is any sludge type build up under either of them. Or check for oil in your anti-freeze.or if your antifreeze is low.