Saab 9-5 Piston Failure

Saab introduced its first-generation (1997 through 2002) 9-5 to the driving public in 1997. In 1999, Saab engineers noticed that the four-cylinder 9-5 models were exhibiting a high engine failure rate. In December 1999, Saab issued a technical service bulletin (No. 210-1991) to its dealers.

Oil Starvation

Saab engineers and service technicians had observed a trend of oil starvation in the 9-5. Pistons sustained damaged when the engine was starved for lubrication. The piston head would break off, and the connecting rods would penetrate the engine wall, thus destroying the engine.

Shaft Busing Problems

Failure of the rear balance shaft bushing also contributed to piston failures. The rear balance shaft bushings would wear out and cause poor oil circulation. This wear would reduce the pressure produced by the oil-squirting nozzle in the piston head, which in turn would reduce the lubrication between the piston head and cylinder wall, causing excessive clearances between the balance shaft and the engine block bushings.

Oil Pump Problems

Saab engineers identified the problem as the oil breaking down into small, soft carbon particles, which would end up in the strainer of the oil pump, where they would accumulate and restrict the flow of oil to the rest of the engine. The remedy for this buildup involves removing and cleaning the oil pump strainer or replacing the strainer.

References

• The Saab Site: Piston Issues Caused by Balance Bushings
• The Saab Pros: Sludge
• Serious Saab: Oil, sludge, strainers and breather systems in 4 cylinder SAAB petrol engines: a study

Resources

• Saab USA: 9-5s