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Thread: Car stuff - possible causes of whirring/humming noise

  1. #1

    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:
    1. 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.
    2. 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.
    3. 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 I replaced it and one sound seems to have been replaced by another (a quieter sound maybe was obscured by a louder one).
    4. 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.

  2. #2
    flat spot you'll likely feel in the wheel long before it makes a sound. whirring sounds wheel bearingy personally. CVs usually are a knocking sound that varies with load and speed. with a manual you can sometimes do good trouble shooting by pushing in the clutch and seeing if it changes while varying both engine and vehicle speed. if it changes while slowing down with the clutch pushed in and the engine idling, you know its running gear related, if it changes while vehicle speed is mostly constant and you rev the engine, then you know its engine/trans related.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  3. #3
    How many miles are on it? Could just be that old VW tranny whine my old tdi whined like a toddler,

    Might need a fluid change. Inner CV usually is a clunk as Cockerpunk said. They kind of suck to replace need those triple square drives, though when I was under my friends MK7 a few weekends ago it looked much easier to get to hers than my old mk4

  4. #4
    Okay, so it's not the CV then, as there's no clunking. I'm hoping it's not a wheel bearing as I already replaced it (twice).

    It is a manual and the sound changes with wheel speed, not engine speed. And it is a MK7, so it's not terrible to work on and I already have triple square tools. And it has about 38,000 miles on it now.

    You guys don't think it a warped rotor could be loud enough to make a sound rubbing against (OEM) brake pads? And what about the diff? Hitting the curb and also impact gun-ing the axle bolt on and off would put some impact loads on both the CV axle and diff, and although I assume those components are pretty tough, I don't really know how tough.

  5. #5
    warped rotor isn't gonna make noise. warped rotors also arnt really real BTW.

    sounds like its in the hub/wheelbearing/halfshaft/output of the trans somewhere.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  6. #6
    Okay, then I can rule that out. And what do you mean by they're not real? Like a brake rotor with run-out isn't a problem?

    Fuck it, if it's the wheel bearing or halfshaft, I'll let it go and see if it gets worse before I start throwing parts at it.

    Thanks for your input, Gordon and Andrew.

  7. #7
    https://www.brakeandfrontend.com/warped-rotors-myth/

    a pulse in the brake petal is from non-uniform pad transfer, not a warp. the pads both float, only thickness variation (caused by unequal wear, caused by non-uniform pad transfer0 is what cuases the problem called "warped rotors"
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  8. #8
    Oh, I see. That's good to know.

  9. #9
    Insider Pump Scout's Avatar
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    38k miles, what year? If it's in the drivetrain, take it in, as long as you're within the warranty time. No point dinking around with something the manufacturer will fix under warranty.

  10. #10
    Put the front end up on jack stands, chock the wheels & put it in neutral. You can now manually manipulate the wheel, checking the wheel bearing, CV joint ,tie rod ends, etc. Costs nothing but 30min total and you will get piece of mind while you find or eliminate possiblities of what the noise is.

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