* Cracks: These are a major problem. Heat cycling (repeated heating and cooling) weakens the plastic over time, leading to stress cracks, particularly around the runners or mounting points. These cracks can cause vacuum leaks, leading to rough running, poor performance, and potentially even engine damage.
* Plastic Degradation: The intake manifold on many 2002 Impalas is made of plastic. Over time, exposure to heat, chemicals (like oil and coolant), and UV light can cause the plastic to become brittle and prone to cracking or warping.
* Gasket Failure: The intake manifold gasket seals the manifold to the engine block. A failing gasket can lead to vacuum leaks similar to a cracked manifold. Oil and coolant leaks can also occur. This is often a cheaper fix than a new manifold.
* Coolant Leaks: Internal coolant leaks within the manifold itself are less common but can lead to overheating and reduced engine performance.
* Improper Installation: If the manifold was ever removed and reinstalled improperly (incorrect torque on bolts, damaged gasket), this can contribute to cracking or leaking later.
* Manufacturing Defects: While less frequent, there's always a chance of a manufacturing defect that weakens the manifold's structural integrity from the start.
It's important to note that the specific cause will depend on the vehicle's history and maintenance. A visual inspection of the manifold is often the first step in diagnosing the problem. Look closely for cracks, signs of warping, and leaks around the gasket.
