Engine oil can leak from the valve cover, and [can leak] due to maneuvers such as hard braking, the March 12 recall summary states. If the oil reaches the hot exhaust manifold, it may ignite, causing an underhood fire. GM said it planned to send a customer advisory letter March 13 to each involved customer of record, explaining the situation and providing precautionary measures that a customer can take until the vehicle is repaired.
Although GM plans to offer repairs free of charge, the recall summary states that until sufficient parts become available to repair all of the 207,542 affected vehicles, the company recommends owners observe the following precautions:
- That owners do not park their vehicle in a garage, car port or other structure.
- If owners notice a burning odor, they should have their dealer inspect the vehicle, which the dealer will do without charge.
- Use premium fuel (91 octane or higher) in the vehicle as recommended in the vehicles owner manual.
The NHTSA opened a preliminary evaluation in January 2007 based on 21 customer complaints alleging engine compartment fires after their vehicles were turned off. GM began an investigation.
According to a more detailed letter that GM send to Buick and Pontiac dealers, the fires may be caused by drops of engine oil being deposited on the exhaust manifold through hard braking. If the manifold is hot enough, and the oil runs below the heat shield, it may ignite into a small flame, and in some instances the fire may spread to the plastic spark plug wire channel. Most cases have occurred five to ten minutes after the vehicle has been turned off.
The letter states that the technical service bulletin repair process for the recall includes replacing the supercharged engines front rocker cover gasket, removing the spark plug channel retainer and installing new spark plug retainers outlined in the bulletin.
According to the letter to dealers, GM is aware of 267 fires, including 17 that involved structure damage. Five minor injuries and one moderate injury have been attributed to the fires. The rate of occurrence was about one in 1,000 vehicles.
Because the vehicle was designed to run on 91-octane fuel, using lower-octane fuel increases under hood temperatures during operation, GM said in its letter to dealers, explaining why the recall emphasizes using premium fuel.
After the repair is complete, the customer will be able to park their car in their garage, car port or other structure, GM stated.