Overheating and no heat inside vehicle

Replace the bad thermostat you bought.

bad thermostat

This can be a few things, for starters most common in my experience is when you have air bubbles in the coolant system (Mostly when its been recently drained or flushed) You will have no heat. Also, if your heater core has failed (in most cases water will leak from under your dash) you will loose heat and your vehicle will most likely overheat. Last but certainly not least, a failing head gasket could cause combustion to leak into your coolant system causing air bubbles which could make your heater not work which could also cause overheating in further along failing head gaskets. Things to check would be a leaking heater core under the dash, overheating, check engine lights and bleeding the coolant system.

look at the boots for the tie rod ends if there wet the steering rack is leaking internally

hello! I had the same problem with my 2000 Pontiac Sunfire... there might be one of these 2 problems with it.... maybe the Heater Core is jammed and the coolant dosen't flow thru the engine to cool it off, or the water pump is defective.... does the heating works or not? if yes, the water pump is defect, if not, the heater core is jammed, try a ''radiator hose cleaner'' (sold in Napa's or Carquest..) it will act as a kind of ''decloaker''.. if works, good! 15$ solution... if not, replace Heater Core... ~150$

With blower on high and tempature to max heat check to see if you have good air flow in all mode selections (defrost, vent, floor etc.). If so and you still have no heat then check heater core hose going from engine to inside car to heater core with vehicle running and coolant tempature about half on guage. If both hoses are hot and coolant in radiator/overflow bottle is full then hot cold blend door is stuck in cold position. If coolant level is low you will get no heat, check coolant level first.

Hello, pgen0315 and thank you for asking your question on Fixya!

Here is a simple process that will walk you through a few steps that will pinpoint the overheating problem on your 1996 Pontiac Sunfire, without even using any tools. It has helped millions of people, and I am certain that it will help you, because I wrote it for people in your exact situation.
How to diagnose your overheating 1996 Pontiac Sunfire

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Thanks for the vote, and good luck!

First of all, make sure the heater core isn't air locked. With the engine running, and your heat temperature on high, loosen one end of the heater hose and see if you can get the air out of it.

Replace the thermostat. It will be fine after that. I know thats what everyone says anytime there is an overheating problem but in this case with the way the system works and it has been working fine up to this point, it's gonna be the thermostat.

problem #2 sounds like you need a blower motor resistor.