My "96 has been losing a bit of coolant somewhere and I wondered the same thing.
I had visions of dumping some of that silver powdery stuff in the reservoir and having it clump up in there.
I found some liquid based leak sealer at AutoZone. The directions recommend using 1/2 the container for a 4 cylinder engine. I added it to the reservoir and it seems to be working.
However, don't make the same mistake I made. I forgot to shake the bottle well before starting to dump it into the reservoir. There IS a semi solid component to that stuff. When I put it in, what came from the bottle, following all of it's liquid part, can only be described as looking like a "dog gift" that you would clean out of your yard. I had to guestimate how much of that "gift" was about 1/2 of what was in the bottle. Thankfully, it seems to have dissolved readily in the coolant.
If I end up using the rest of it, I'll be sure to add a little coolant to the bottle and shaking vigorously!
FriPilot
There isn't one. Access to the radiator is via the reservoir.
When the engine is cold, check the level of the coolant in the reservoir. Make sure it's up to the mark on the side. Make sure you get the reservoir cap on tight.
On top of the reservoir on the passenger side of the motor. It will say Caution do not remove when hot!. There is not one located on top of the radiator itself.
I looked and looked for one on my '96. I swear it doesn't have one. I believe that all fluid adding must be done via the reservoir.
Look at the lower or rear of radiator
Open the hood on your Sunfire. Remove the radiator cap from the radiator overflow bottle. Turn the engine on in the Sunfire, and let the engine run for no less than 15 minutes. Set the dials on the heater control panel to full fan speed, full heat, and front defrost positions. This will speed up the processes of heating the engine to full temperature. Removing the radiator cap and performing these procedures will allow the pressure in the engine to build up. As the pressure gradually increases, the weight of the coolant will force air bubbles out through the radiator overflow bottle hole. This process is called bleeding the cooling system. Turn the engine off when you notice that there are no more bubbles coming from the radiator overflow. Top off the radiator overflow bottle with fresh coolant. Use 50/50 diluted, universal coolant to fill the overflow. Replace the radiator cap when the reservoir is at the "Full" mark. http://www.ehow.com/how_7734216_bleed-system-Pontiac-sunfire-22l.HTML
it's getting too cool, really
It is in the lower radiator hose
Yes it will.
The radiator cap is on top of the radiator. It is located near the front of the engine compartment towards the right side of the car.
A radiator is not an electronic part, thus is not fused.
A Haynes or Chilton manual will have detailed instructions on how to get that radiator out. I highly recommend that you pick one up. I think they're about $17.