low coolant light comes on..

when i first start my car up and start driving, my low coolant light will come on. I obviously assume i'm low on coolant, but after a few minutes the light will go away. the light usually goes away though in a few minutes. the tank is still full also..any idea why this is happening?

If it's low enough it might come on because the coolant is cold, then as it warms up it expands and might be just high enough to turn the light out. Try adding a spit of coolant to the tank.

i don't think water expands..

Have you tried bleeding air out of the system?

i don't think water expands..

Your coolant/water mix expands with heat. That is why there is typically a "cold" full mark and a "hot" full mark on the tank. Almost every fluid in an automobile expands with heat. FYI