One problem related to engine head gasket failure has been reported for the 1998 Cadillac Deville. The most recently reported issues are listed below.
Dealer reports that this gasket failure is a common problem with the northstar engines and that the entire engine must be dissassembled to replace the gaskets. The failure allows excessive amounts of oil to leak out of the engine leading to eventual failure. The problem seems to be poor or faulty engineering of the engine.