Car stuff - possible causes of whirring/humming noise
This is not exactly the right place to ask this, but VW forum users are generally idiots.
What are possible causes for a whirring/humming sound that seems to be coming from the front of my GTI? It's a relatively quiet, intermittent, faintly metallic sound that changes with speed. It's not loud enough that I think there's an issue, but I'm kind of anal and would like to at least figure out where the noise is coming from.
I've checked:
- Brakes. The rotors are slightly warped, so they contact the pads once per revolution when I have the car up in the air and spin the wheel. This is my best guess.
- Tires. They're about 80-90% dead, with one tire in particular just reaching the wear bars. I did lock up that wheel in the rain once, so there might be a slight flat spot. This is my second guess, but I swapped this wheel to the rear and the sound still sounds like it's coming from the front of the car, although that could be an illusion. The sound seems slightly too metallic to be a tire though. I'll know better once I put new rubber on.
- Wheel bearing. In the case when I locked up the front wheel, I understeered into a ramped curb at moderate speed (maybe 20 mph) and think I damaged that wheel bearing. I replaced it and one sound seems to have been replaced by another (a quieter sound maybe was obscured by a louder one).
- Outer CV joint. When replacing the front wheel bearing hub assembly, I sprayed WD-40 into the splines to loosen the axle without realizing that this car's axles have an open hole between the axle bolt hole and the CV joint. So the CV grease was loosened up by the WD-40 and it was a couple days before I could pull the boot back and clean/regrease the joint. This could be the culprit, but it seems like CV joints are pretty tough and I don't hear a change in noise when turning.