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strange noise at cold start 850

posted by  someone claiming to be slimV on  Tue Jul 19 06:31 CST 2005 [RELATED]

my 96 855T has been making a really wierd noise which only happens at cold start up (usually in the morning). it almost sounds like the noise a fuel pump makes when it is failing, a low pitched howl or whine. the noise gets slightly louder as the RPM's increase, or on acceleration, but after 5 minutes of running time (even if the engine is still registering cold) it goes away.

anyone want to take a stab at this?








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    strange noise at cold start 850

    posted by  someone claiming to be marty on  Tue Jul 19 10:47 CST 2005 [RELATED]

    I notice this low pitched "howl" also ..... if you don't think that it's a major item, such as the timing belt tensioner or idler pulley, you may just be hearing the air pump at work.... it's part of the emission control system, and shuts itself down once the exhaust system is up to temperature... the engine temperature is not the determining factor. The air pump operates only to control low temp start-up emissions, and is such a common source of concern, that it's even mentioned in some of the fine print in the Volvo owners manuals.
    Good luck

    Marty

    '96 855T








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    strange noise at cold start 850

    posted by  someone claiming to be ksg on  Tue Jul 19 08:45 CST 2005 [RELATED]

    Why not listen with a length of hose or tube to localize the noise? You can get fairly close to all the serp belt components. You could also remove the upper timing belt cover. Just use lots of care so the tube or any part of you doesn't foul on anything and injure you or the engine. A soft tube (rubber hose) doesn't transmit sound as well but would be safer.








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    strange noise at cold start 850

    posted by  Erwin on  Tue Jul 19 08:22 CST 2005
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    last visit: Thu Oct 23 10:39 CST 2014
    [RELATED]

    It may be the "normal" howl that's been discussed many times in the past. My 95 855t has been doing this since I bought it 3 years ago with 83,000 miles. The T-belt and tensioner had been changed btw and it's at 115,000 now. I'm not going to say they can't be the source though, just not sure about it being a warning of imminent failure. It's been called the "ghost" before and is more noticeable in cold weather. It follows engine rpm for about 3 minutes then fades away. Usually by the time I drive from my house to the on ramp, about half a mile, it's gone.

    Erwin in Memphis








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    strange noise at cold start 850

    posted by  someone claiming to be AJU on  Tue Jul 19 08:20 CST 2005 [RELATED]

    Classic air pump noise.








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      strange noise at cold start 850

      posted by  Rule 308 on  Tue Jul 19 18:32 CST 2005
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      last visit: Tue May 8 09:20 CST 2012
      [RELATED]

      An air pump will usually only run for a max of 100 seconds and it's pitch is constant and does not increase with engine RPM. A seizing tensioner or idler pulley on the other hand will howl big time, only when cold, and will go away after a few minutes. The one that I changed out last week was the timing belt idler pulley and it was so bad that it would barely turn in one direction and locked up solid in the other. It was only a matter of time before it seized up entirely and burned the belt off.

      Get it stone cold and take the timing belt cover off and then fire it up. A half ways decent set of mechanic's stethoscopes are cheap at the local Harbor Freight. With it running carefully stick your probe into the center of each bearing where it is bolted down and not spinning. It should be real obvious which one is the culprit.

      Mark








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    strange noise at cold start 850

    posted by  Rule 308 on  Tue Jul 19 07:14 CST 2005
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    last visit: Tue May 8 09:20 CST 2012
    [RELATED]

    Idler pulleys and tensioner pulleys for the serpentine belt and or the timing belt. I would get them changed asap.

    Mark








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      thanks to all for the help!! n/m 850

      posted by  someone claiming to be slimV on  Tue Jul 19 15:42 CST 2005 [RELATED]

      n/m







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