Where is the thermostat located on the 1993 Buick Century?

Did you get all the air out,remove radiator cap,start up.let run until the thermostat opens,you will see the flow in radiator,put cap back on and fill overflow container to full.

head gasket maybe air in system fill to the top and start engine let run till all the air in the system comes out it will push water out keep adding water till it takes a big drink and stops pushing water out

Do you know for a fact the gauge is correct ?
Could be a circulation problem such as thermostat or water pump, low on coolant, faulty gauge, or other problem.

If you are talking about the coolant over flow??? You may have a bad radiator cap, maybe low on coolant, maybe thermostat. You haven't provided a lot of details here so it's hard to say for sure.

it sounds like one of several problems radiator needs flushed , water pump is bad or going, thermostat is bad, pin hole in one of the hoses, cracked head, hole in radiator, hole in heater core.if core is leaking you will notice water on the floor inside the car on pasenger side. if radiator has hole when you fill radiator with coolant it will leak froom fins sometimes only when hot. thermostat bad your car will read hot and or cold always. if stuck open cold, if stuck closed hot, after about 15 20 mins of running engine will cause radiator to boil over to over flow tank.never open radiator cap when engine is hot :) burn hazard.if pump is bad or going will notice gauge reads hot intermittent or always. will boil in to overflow tank. if head is cracked will notice water comming from side of engine block or in oil when you change oil. if radiator needs to be flushed will notice scale or gunk on radiator cap
(if you think you need help or do not have tools to perform please take to a machanic)

When sitting still, yes both fans on a car equipped with two fans will run. The temperature ranges you posted seem within acceptable range. That said, the water (coolant) should not boil at those high temperatures, but some overflow is expected/normal. Ensure that you are not adding pure water to the radiator and instead are premixing it with antifreeze coolant or adding premixed 50/50 that you can buy at auto stores as this will keep the water from boiling and freezing.

As an added point of information, the hose leading into the overflow jug is two-way, meaning that when the coolant in the radiator cools down enough, it creates a vacuum and pulls coolant back into the radiator.

Zach

The thermostat is in a housing on the engine. It's located where the lower radiator hose attaches to the engine. The coolant level should be right near the top of the radiator when you remove the cap, and the overflow canister should be filled to the indicated line (there are markings on the canister). If your gauge stays on cold, you may have a faulty coolant temperature sensor. If it will get to normal operating temperature while sitting still, but starts cooling down when you drive, you have a thermostat failure - it's stuck open, and will need replacement.

Have you changed the thermostat? The way you describe it seem like a thermostat.

I have a 1997 Buick Century with the same problem. Both my fans work if the A/C is
on as they should. If your turn off the A/C the passanger side fan will not come on
and at an idle the coolant in the radiator will boil, you can hear it in the overflow tank.
If you are driving there is enough air flow thru the radiator that the coolant doesn't
boil and the car doesn't overheat. I have replace the water pump, the thermostat.
and the ETS or engine temperature sensor mounted just above the thermostat in
the thernostat housing, to no avail, I still have the same problem. The only other
thing is the coolant level sensor in the radiator, which I haven't replace yet due
to the fact you have to pull the radiator in order to replace it, which is a major
undertaking. I have a low coolant indicator on all the time on the dash so I have
a pretty good idea the coolanat level sensor is bad. The coolant level is not low
so that sensor is not working as it should. I hope this may help with your problem.
To test you fan raise the hood when it is cold and top off the radiator and fill the
overflow tank to the cold mark. Start the car and let it idle with the A/C off and
see if the drivers side fans comes on. It will have to get to operating temp
before the fan will come on. If it doesn't come on replace the radiator low coolant
sensor on the passanger side of the radiator. If that doesn't fix the problem
replace the thermostat and the Engine Temperature Sensor at the thermostat
housing with an A/C Delco Engine Temperature Sensor. Good Luck..