Symptoms suggesting a bad intake manifold gasket:
* Rough idle: This is a very common symptom. The gasket's job is to create a tight seal, and a leak allows unmetered air to enter the engine, disrupting the air/fuel mixture. This leads to an uneven idle, sometimes accompanied by shaking or vibrations.
* Vacuum leaks: A failing gasket will cause vacuum leaks. You can test this with a vacuum gauge (the easiest way) or, more crudely, by spraying a carb cleaner or brake cleaner around the intake manifold gasket while the engine is running. If the RPMs change, you've likely located a leak. Caution: Be extremely careful when using flammable sprays near a hot engine.
* Engine hesitation or stalling: Similar to rough idle, an inconsistent air/fuel mixture due to a leak can cause the engine to hesitate during acceleration or even stall.
* Check engine light: A bad intake manifold gasket may trigger a check engine light, though this isn't always the case. The code retrieved will be helpful in pinpointing the problem.
* Loss of power: The engine might struggle to reach its full power potential if there's a significant vacuum leak.
* Coolant leak: While less common, a very bad intake manifold gasket can leak coolant, as it sits between the intake manifold and the engine block. You might see coolant pooling around the intake manifold or notice a loss of coolant in the reservoir. This is often accompanied by a sweet smell from the coolant.
* Exhaust smoke (white or gray): In severe cases, you might see white or gray smoke emanating from the exhaust, indicating coolant is leaking into the combustion chambers.
How to check:
1. Visual Inspection: Start with a visual inspection of the intake manifold. Look for signs of coolant leaks, cracks, or obvious damage to the gasket itself. This often requires removing some components for a better look.
2. Vacuum Gauge Test: This is the most reliable method. A vacuum gauge connected to a vacuum port on the intake manifold will show fluctuating or low vacuum readings if there's a leak. A steady vacuum reading indicates a good seal.
3. Carb/Brake Cleaner Test (use with extreme caution!): Spray the cleaner around the suspected leak areas (joints between the intake manifold and the engine block) while the engine is running. A change in RPM indicates a leak. Again, be extremely cautious with flammable sprays near a hot engine.
4. Professional Diagnosis: If you're not comfortable performing these checks, take your Lumina to a mechanic. They have the tools and expertise to diagnose the problem accurately. They'll likely use a pressure or smoke test to pinpoint leaks.
Important Note: Replacing an intake manifold gasket is not a trivial task. It often requires removing various components, and you'll need a torque wrench to tighten the manifold bolts to the correct specifications. If you're not mechanically inclined, it's best to have a professional handle the repair.
