Which symptom is commonly associated with a worn timing belt?

A worn timing belt can lead to difficulty starting the engine primarily because the timing belt is crucial for synchronizing the engine’s camshaft and crankshaft. If the timing belt has worn, stretched, or has broken teeth, it can impact the timing of the engine, leading to incorrect valve timing and an inability to start the engine effectively. This misalignment means that the air-fuel mixture may not enter the engine at the correct time, preventing the engine from firing up.

Additionally, other symptoms can occur as the belt continues to wear, such as misfires or rough running, but the immediate and noticeable effect often manifests as starting issues. Proper timing is central to the engine's operations, making this symptom closely tied to the condition of the timing belt.

In contrast, the other symptoms listed are not directly linked to the timing belt. Increased oil consumption typically relates to internal engine wear or issues with seals. Excessive tire squealing usually indicates problems with the wheels, tires, or suspension, rather than issues with the timing belt. Cooling system leaks are associated with components like hoses or radiators, not with the timing belt itself.