Buzzing Noise:
* Description: The buzzing noise increases in pitch when you accelerate and decreases when coasting. It seems to correlate with RPM changes.
* Potential Causes:
* Alternator: A worn or failing alternator can produce a high-pitched whine or buzzing noise, especially under load (acceleration).
* Power Steering Pump: A worn power steering pump can also create a buzzing sound, especially when turning the wheel.
* Belt Tensioner: A loose or worn belt tensioner can cause belts to slip and create a buzzing sound.
* Other Accessories: Sometimes, other accessories like the air conditioning compressor can make noises when they are faulty.
* Wheel Bearing: A worn wheel bearing can create a buzzing or humming noise that changes with speed.
New LF Axle Inaudible at 65mph:
* Description: You mentioned a "new LF axle". This likely means you replaced the left front axle recently. It's inaudible at 65mph.
* Potential Causes:
* Improper Installation: If the new axle wasn't installed correctly, it could be causing a vibration or noise that's only noticeable at certain speeds.
* Defective Axle: It's possible that the new axle itself is faulty.
* Other Issues: The noise could be related to something else entirely, like a wheel bearing or CV joint, and the new axle isn't the culprit.
Troubleshooting Tips:
1. Listen Carefully: Pay close attention to the buzzing noise. Does it change with engine RPM or vehicle speed? Can you pinpoint where the noise is coming from?
2. Check Belts: Visually inspect the belts under the hood. Are they loose, cracked, or worn?
3. Inspect Alternator: Look for signs of wear on the alternator belt, or check the alternator for any signs of damage.
4. Power Steering Pump: Listen for any unusual noises coming from the power steering pump when you turn the wheel.
5. Wheel Bearings: Inspect the wheel bearings for any signs of wear or damage. Jack up the car and try to move the wheel up and down. If there is any play, the wheel bearing may be worn.
6. CV Joint: Check for any signs of damage or excessive wear on the CV joint on the left front axle.
7. Re-inspect Axle Installation: If the new axle was installed recently, make sure it's securely installed and properly lubricated.
Recommendations:
* Mechanic Inspection: It's best to take your Forester to a trusted mechanic for a proper diagnosis. They can listen to the noises, inspect the components, and identify the root cause of the issues.
* Don't Ignore the Noise: Don't ignore the buzzing noise, as it could indicate a potential problem that could worsen over time.
Remember, a mechanic will be able to give you the most accurate assessment and recommendations. Good luck!
