There are a few possibilities 1) your resivoir tank is cracked and leaking 2) your sending unit is covered in gunk or corroded 3) your sending unit is defective and needs replacing 4) you are leaking coolant from somewhere (bad hose, bad gasket, bad joint, etc)
Water is an acceptable quick fix, and tap water is fine (that is what you flush it out with). Once your problem is sufficiently solved, I would recommend a complete drain/flush/refill of your radiator with the proper mixture of coolant.
Answer
With the 5th generation Monte Carlos, when the overflow tank is emptied, and it kicks the sensor on, after you fill it up, the sensor may not reset or turn off and GM had problems with those sensors and they normally had to be replaced. It sounds like a bad coolant level sensor to me.
Check your coolant level...
If coolant full could be a bad sensor
It means it might need coolant, if not than you should probably see a mechanic.
The low coolant sensor is bad or disconnected.
Check coolant level in recovery tank Perhaps a bad sensor. Sensor located in coolant recovery tank
How do you take a rheostat out of a 2003 monte carlo
i have a 2004 chevy monte carlo and the service engine soon light is on what does it mean?
did u bleed the coolant system of air cuz that could be the reason
Changing the brake light switch in your Chevrolet Monte Carlo is quite simple. The brake light switch simply plugs in and out.
Did you change the radiator? If you did you might have the wrong one,without a full provission for the sensor. If you did not the plug might be disconnected or faulty.
You have to have a computer programmer module, from O'Reily's or Autozone to reset it. Some will let you do it and some say that they are not authorized to do it. Good luck...
genarally needs topping up with water ?????