It only blows smoke on start up till it warms up. I am also losing coolant, and oil. I had issues with overheating a while ago, and think I may have blown valve seals.
Why is my caddy blowing smoke when I first start it? on 1997 Cadillac DeVille
very likely a northstar head gasket issue - google it and you'll find it's a very common northstar engine problem. take a look at http://www.northstarperformance.com/ for more on this problem.
2 more answers
YOU MAY HAVE BLOWN HEAD GASKETS. ONE SIGN IS YOUR OIL WILL LOOK LIKE A CHOC MILKSHAKE. THE OTHER IS WATER IN COMBUSTION CHAMBER. AFTER CAR IS COOL REMOVE ALL SPARK PLUGS AND SEE IF WATER COMES OUT OF ANY CYL WHILE CRANKING. YOU CAN ALSO BUY A HEAD GASKET CHEMICAL TESTER AT AUTOZONE
Possible a cracked head gasket!