I put about 1 and a 1/2 gallons of coolant in my
1996 Chevy blazer this morning and it is still
running hot what's the deal.
Sounds like you have a leak. You have to address that first. The cooling system is a closed pressured system, so if you have a leak, low coolant level and air gets in and causes an overheat condition. Check the radiator, hoses, reservoir, etc.
If you are losing coolant there's a few places it could be coming from. A hose, waterpump or thermostat housing, or freeze plugs. It could also be your thermostat gone bad.... that's the cheapest place to start. Could be your water pump gone bad. Test your thermostat by putting it in boiling water. It should open at 180 degrees Fahrenheit. Is your car smoking from the tail pipe after warming up? And if so does it have a sweet smell... that's a blown head gasket or cracked head... overheating can cause this.