I have just used the stuff to fix my cooling system. Expansion tank cap has a slight leak in it so wrapped it around cap where it meets the bottle and all sealed again until I get a new one tomorrow. Sure I probably could drive around like this for awhile but filling coolant level could become an issue and a new cap is only about $15
Not the greatest of photos but you get the idea the loose end is cause it was the end of the roll the cardboard residue preventing it from sticking 20140803_172518[1].jpg