Cadillac Repair: overheating northstar, head gasket, sparkplugs

Question
I have a 99 concours deville. It overheats very quickly. There is no antifreeze in the oil or transmission fluids. There are no puddles under the car. It loses about a gallon of antifreeze every 5 or 6 miles. Any ideas?

Answer
Hi Mike, You'd think that looseing that much anti freeze would show up somewhere. Sounds like you might have a bad head gasket. If it runs rough upon first start of the day then removing all the sparkplugs after an overnight sit and before it is started should isolate what cylinder the coolant is going into. Then it is a matter of  disassembling the engine to determine what needs fixing. Hope that helps. Bill