Here's why:
* Valve Cover Gaskets: These gaskets seal the valve covers, preventing oil from escaping. If they're worn or damaged, oil can seep onto hot engine parts, vaporize, and create smoke when the engine is shut off. The smoke will often be bluish-white.
* PCV System: This system vents crankcase pressure and blow-by gases. A malfunctioning PCV valve or clogged hoses can cause excessive pressure buildup, forcing oil mist out of various seals or openings, leading to smoke upon engine shutdown. Again, the smoke would likely be bluish-white.
Other less likely, but possible, causes include:
* Leaking Exhaust Manifold Gasket: While less likely to produce smoke *only* after shutdown, a severely leaking exhaust manifold gasket could allow combustion gases to escape and leave a residue that burns off later, creating a small puff of smoke. This smoke would likely be grey or white.
* Overfilled Engine Oil: An overfilled engine can cause oil to be flung into hotter areas of the engine, resulting in burning and smoke.
* Faulty Head Gasket (less likely): A failing head gasket is more likely to show other symptoms (like overheating, coolant loss, white smoke during operation) but could contribute to some smoke after shutdown in severe cases.
To diagnose the problem:
1. Check the oil level: Is it significantly overfilled?
2. Inspect the valve covers: Look for oil leaks around the gaskets.
3. Inspect the PCV valve and hoses: Are they clogged or damaged? A simple test is to remove the PCV valve and check for free movement. The hoses should be flexible and free of cracks or blockages.
4. Check for leaks around the exhaust manifold: This is harder to do while the engine is hot, so wait for it to cool down completely.
If you're not comfortable performing these checks yourself, it's best to take your Oldsmobile to a mechanic for diagnosis and repair. Ignoring the problem could lead to more serious engine damage.
