This is usually due to a faulty sensor in the coolant bottle. It could also be a bad connection.
I had same thing happen to me on trip from Missouri to Wisconsin at night time.
Stopped to check and nothing low
It was connection at sensor
Squeezed it with plyers and havent had problem again for over 5 years now
troubleshoot the coolant on a 1999 oldsmobile intruge
Liquid coolant
for gods sake - read the bloody owners manual It used to be dexcool {orange} but G.M. has had some problems with that. I use a universal coolant I get at wall mart.
Why is the electric coolant fan in your 1989 Oldsmobile cutlass cierra not working?
red coolant use the dexcool
A 2000 Oldsmobile Alero with a 2.2 engine will hold approximately 13 liters of coolant. Adding coolant to your vehicle is very important.
Either your coolant is actually low or you have a coolant sensor bad.
beside thermostat
12.3 quarts
Dex-cool prestone
At the bottom of the radiator on the passangers side.
to cool the coolant in the engine