My grandpa has a 91 Deville. Here is the problem the coolant is overflowing out the recovery tank. It is also low on oil. He thinks its a blown head gasket. There is no sing of burning oil. Or any coolant in the oil pan its self. still has all its power dosn't even run rough. I think its a matter of checking the oil and a bad radiator cap that is the problem. Any ideas would help thanks