I have a brown residue in my over flow tank and also in the top of my radiator,is possibly a blown headgasket?
Problem with cooling system on 1997 Chevrolet Astro
GM was putting something called Stop Leak Tablets in their cooling systems from the factory. This residue may be due to the tablets. Check the oil and see if it is a milky white color. This will let you know if the oil and coolant are mixing. IE: head gasket, intake gasket, etc.. If you are still worried you can rent a compression tester from an auto store and check compression on each cylinder. If you had a blown head gasket this would affect the drivability of the vehicle.