Coolant light stays on all the time. on 2000 Pontiac Montana

Coolant light stays on. Coolant slowly decreases; but the light stays on even when I add the coolant. Some dirty specks appeared in the coolant compartment. Does a mechanic need to change this fluid? Gasoline gauge is wacky on dash as well. Are these related?

Asked by for the 2000 Pontiac Montana
i had the gas guage replaced in my 2000 montana. apparently they are a common problem. another common problem is with the engines. they are bad for intake gaskets, which could explain the coolant loss and light on.