I have a 1997 sts seville. When i drive for awhile i seem to be loosing coolant. If i drive for an hour it usually needs about a gallon of coolant. I cant find a leak or anything anywhere. Oil looks fine and i never find anything under car or in motor compartment.
coolant on 2005 Cadillac STS
You probably have a blown head gasket, check the oil to see if there is a tan to brown milky substance on it and if it does the head gasket will need to be replaced. you can get an estimate here www.repairpal.com/estimator and find a shop here www.repairpal.com/directory