The exhaust center muffler can fail causing excessive exhaust noise from under the center of the vehicle.
1999 Saab 9-3 Problem Reports
RepairPal Verified 1999 Saab 9-3 Problem Reports
The head gasket can fail causing the coolant and oil to mix in the engine, and external oil leaks around the cylinder head and block. Symptoms can include overheating, white smoke from the tailpipe at start-up or acceleration, and the visible presence of oil in the coolant expansion tank.