* Alternator: This is the top suspect. As the alternator gets hot, a worn bearing or a failing diode can create a buzzing sound. The increased electrical load from acceleration might temporarily mask the noise by changing the alternator's behavior.
* Power Steering Pump: A worn bearing in the power steering pump can also buzz, especially when warm. The increased pressure from accelerating might momentarily reduce the noise. This is less likely to completely stop the buzzing, but it's worth considering.
* Idler Pulley or Tensioner Pulley: These pulleys guide the serpentine belt. A worn bearing in one of these can produce a buzzing or whining sound that changes with engine speed and load. The noise might become more pronounced once the engine and pulleys are warmed up. The acceleration might slightly alter the belt tension, reducing the noise temporarily.
* Exhaust Leak Near a Heat Shield: While less likely to be buzzing specifically, a heat-related exhaust leak near a metal heat shield *could* create a buzzing or rattling sound that changes with engine load (and might be more pronounced when warm).
* Loose Electrical Connection: Less likely to be a consistent buzz, but a heat-related expansion of a loose electrical connection somewhere in the engine bay *could* cause a buzzing sound that changes with load.
Troubleshooting Steps:
1. Listen Carefully: Try to pinpoint the location of the buzzing sound. Is it coming from the front of the engine, near the alternator and power steering pump? Or is it further back?
2. Visual Inspection: Once the engine is cool, carefully inspect the alternator, power steering pump, idler and tensioner pulleys, and serpentine belt for any obvious signs of wear, damage, or looseness. Look for anything that might be rubbing.
3. Listen While Accelerating: Pay close attention to how the buzzing changes when you accelerate. Does it diminish significantly, or does it just change pitch slightly? This will help narrow down the possibilities.
4. Check the Belt Tension: The serpentine belt should have the correct tension. Too loose a belt can lead to pulley noise.
5. Professional Diagnosis: If you can't pinpoint the source, it's best to have a mechanic diagnose the problem. They have the tools and experience to identify the faulty component accurately. A simple test on the alternator (like a load test) can often determine if it's the culprit.
Ignoring this buzzing could lead to more serious damage, especially if it's the alternator. A failing alternator can leave you stranded. It's important to address the issue promptly.
