W203 noise on driving straight, silent on turning!

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by stephenmercedes, Jun 13, 2018.

  1. stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    2001 W203 C240. I have a slight noise when driving, it's sounds almost like a small fan blade hitting an air vent, but it isn't! It doesn't seem to be speed related and maintains a constant volume. However, when I'm going round a roundabout, or turning a corner, it totally disappears! Any suggestions of where I should look?
     
  2. brucemillar

    brucemillar MB Club Veteran

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    It could be the internal AC TEMP FAN/sensor. This uses a small fan behind a tiny grill on your AC head unit to draw air in over the sensor. Try blowing that grill out with some canned air?


    Sent from my iPhone using Tapatalk
     
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  3. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    Just bought a can online, that would be great if it was solved by that...
     
  4. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    Mixed result, I think it got a bit quieter, but I'm not sure, noise is still there! Is it worth shooting a squirt of WD40 into the vent? Would it do any harm?

    (Oh, now know why 'High Street' is disappearing, canned air online £2.50 inc P&P, pop into your local PCWorld/Curry and you'd walk out £13 lighter, yes, I know, for a can of air LOL!)
     
  5. Stratman

    Stratman Hardcore MB Enthusiast

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    It's probably imported air, the kind you can walk on ;)
     
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  6. HITECH

    HITECH Hardcore MB Enthusiast

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    Sounds more like a faulty A/C motor actuator arm. Click click click, maybe go away with g force from rounding a corner..... I wouldn't recommend spraying any kind of grease or flammable liquids in your vent bud. There are tons of threads on air conditioning motors, flaps, broken arms.... have a look. maybe its your problem. maybe not.... Unfortunately I have this problem with mine which means stripping the dashboard apart to change the motor with the broken arm on it.
     
  7. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    Too late LOL I sprayed it last week but it made no difference at all. I've learned to live with it, in the grand scheme of life, there's plenty of other stuff for me to worry about! :)
     
  8. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    Right, thought I'd give this a wee bump as the noise is getting worse (louder), here's a summary:
    1. Sounds like a fan blade rattling or hitting something, but it isn't.
    2. On increasing speed, the noise intensifies but does not change in pitch
    3. Below 10mph, you can barely hear it at all, (but impractical to drive everywhere at that speed!)
    4. When bearing left, or turning left, it totally stops, but continues on straitening up.
    OK guys, let's hear your best shot...
     
  9. andy27168

    andy27168 Hardcore MB Enthusiast

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    Hi,
    Sounds to me as if you have something wrong on the passenger side front wheel/suspension, tyre, wheel bearing maybe, possible worn ARB or suspension bush.
    I would start by jacking up the front removing front wheels, and have a good look, checking for wheel bearing play, use a lever bar and check for wear in the ball joints, excessive play in the suspension arms, check both sides so you can compare any play from one side to the other.
    When putting back swap the wheels from one side to the other (do check tyre sidewall to ensure the tyres are not directional).
    Swapping the wheels should tell you if the tyre is the cause if the noise transfers to the right side.
     
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  10. alecmascot

    alecmascot Hardcore MB Enthusiast

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    Any chance that you can post a recording ?
     
  11. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    mmm...You are speaking to an analogue man in a digital age LOL I could possibly have a go at recording it on my 12 year old Nokia (it does have that function) but the process to then upload it for an analysis may well be a step too far. I'll see what I can do... :)
     
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  12. Stratman

    Stratman Hardcore MB Enthusiast

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    Could it be be that perennial favourite the parking brake cable?

    The plastic retaining clips holding it to the propshaft tunnel become brittle and break, allowing the cable to rub against the propshaft. The noise can stop going round corners as insufficient centripetal force allows it to move away from the shaft, only to rub against it again on the straight.
     
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  13. alecmascot

    alecmascot Hardcore MB Enthusiast

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    That would fit everything but condition #2... does not change frequency with speed.

    If it really does not change frequency with speed then it cannot be caused by any driveline or engine component.
    That leaves us with in-car systems like climate control.....
     
  14. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    OK, We have a WINNER!!! Startman was absolutely 100% spot on with the diagnosis. I brought my car in earlier to my local 'indy MB' garage. The guy took it for a test drive and diagnosed the noise within seconds, confirming it was the parking brake cable clip that had broken.

    He put it immediately on the ramp, repaired same, than replaced my drivers side air vent I've had in the boot for ages to replace the existing broken one where the slats were not operational. He also, on dismantling that part of the dash noticed the handbrake pull lever was cracked, and he replaced it with a spare he had. In addition, he also installed 2 x xenon headlamp bulbs I had in car which I had intended to replace myself at the weekend. Considering I was a 'walk in', the service I received was absolutely outstanding, and the cost, well it was so little I'm a bit embarrassed!

    Belfast area:

    Creevy Autos - independent Mercedes Benz Specialist - Belfast,County Down-Northern Ireland N.I.
     
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  15. alecmascot

    alecmascot Hardcore MB Enthusiast

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    Glad it worked out for you, but you misled all of us when you said it was not speed related......
     
  16. OP
    OP
    stephenmercedes

    stephenmercedes Hardcore MB Enthusiast

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    Not sure how, it got louder as I went quicker (as stated) but to me, it just stayed the same 'noise'. Anyway, all good now...
     

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