Knocking type sound...

Discussion in 'Gen 1 & 2 - Engine, Exhaust, Drive Line & AC syste' started by SableSal, Mar 31, 2009.

  1. SableSal

    SableSal SHO-ABLE Owner

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    Well, this is the story... When starting the vehicle, I can hear a knocking type sound coming from the engine. It doesn't sound like a rod bearing, and honestly if it were a rod bearing it would have demolished the engine compartment by now.

    The knock is coming from up top, and sounds like it's coming from near the runners. Once I get near the runners the sound gets away from me... I think I've pin pointed the sound coming from near the water pump area, although I wanted to get your guys' expertice in the matter.

    The noise happens at all times, seems to get drowned out with acceleration and driving. I normally can't really hear it in the cab. Seems to deminish when the vehicle reaches operating temperature.

    Well, tonight I'm going to use a stehascope to listen as to where the noise is coming from. I figured meanwhile I would have you guys brain storm as to what the noise could be.

    Anyhow, any suggestions would be wonderful!

    Thanks!
     
  2. Ishodu

    Ishodu SHO Member

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    I have seen this happen with a loose harmonic balancer pulley bolt. Check to make sure its not loose and pry that it is tight.
     
  3. JRA2000TL

    JRA2000TL The Complainer

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    Got the same noise. Mine is on the runner/intake bolt right above cyl # 4 (front far left cylinder if standing in front of the car looking at the engine). I loosened and wiggled the intake and it seems to have gotten quieter. The intake may not be properly seated. If extra air gets in there, it can sound like a diesel from what I'm told. Mine also diminishes as the car is warmed up. I've driven my car over 2k miles with that noise, so it's not a rod bearing. I've gotten it up to 7k rpm multiple times too.
     
  4. SableSal

    SableSal SHO-ABLE Owner

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    Very good info... I thought I would have a chance to look into it here today. Looks like Saturday is my day. Keep the suggestions coming!

    Thanks everyone!
     
  5. JRA2000TL

    JRA2000TL The Complainer

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    Let us know what you find. The PO of mine told me he pulled the intake and valve covers and all of the valves were supposedly within specs. I pried the timing cover apart while the car was running (didn't take it completely off), and the t-belt wasn't flapping around. That rules out the timing belt tensioner.

    Put the stethoscope over the "hump" part of the valve cover where the cam tensioner is and see if it's louder there. I've been told that's what's wrong with mine but I am thinking otherwise because mine is concentrated to that one area above cyl #4 only.
     
  6. Racer X

    Racer X SHO Pilot

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    Pull the timing belt cover.

    If you see red dust
    [​IMG]

    and the knocking sounds like this:
    [​IMG]

    You likely have crank cancer.
     
    Last edited: Apr 1, 2009
  7. SableSal

    SableSal SHO-ABLE Owner

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    Well it sounds familiar to that. I'm going to pull the timing cover off this weekend and see what I can find. What's the cure for it? Replacement of the crankshaft? Let me know what you did Hamal.

    Thanks for the info...
     
  8. JRA2000TL

    JRA2000TL The Complainer

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    Wow, your noise is alot worse than mine. Definitely pull that timing cover off and check that. There's a wite up on SHOTimes about what crank cancer is and what it does, I believe.
     
  9. F-22 Raptor SHO

    F-22 Raptor SHO New Member

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    Before pulling anything apart consider the following:

    A knocking noise up top from the rear bank passenger side could be (and often is) the result of the timing belt tensioner pulley being bad. If you rev the motor up slowly and find that the knock goes away above about 2200 rpm then returns as you come back down on the revs under 2200 rpms, here is what is happening: The timing belt is slacked causing a misfire on cylinder #1 which is compensated for as the revs are increased.

    I replaced the tensioner on Bizzy's Green SHO when this symptom appeared in my driveway. Car ran great otherwize.

    Now your crank cancer can be checked when replacing the tensioner as the crank pulley has to be removed when doing this.
     
    Last edited: Apr 2, 2009
  10. Sho-Driver

    Sho-Driver Peter Pan

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    You can always stick a socket on the crank bolt to see if it is loose. You don't even have to jack up the car.
     
  11. Racer X

    Racer X SHO Pilot

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    You mean the crank pulley needs to be removed, right? The crankshaft itself doesn't need to be removed to replace and adjust the timing belt tensioner.

    Sal, I fixed my crank cancer with a 3.2L swap.
     
  12. dodgebusta

    dodgebusta Online/Offline

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    let the kid out from under the hood out, he is hitting the hood because he's getting cramped under there.

    :woo-hoo:

    Serious, I have to say everybody seem to have you on the right track. I'll just sit here and watch your progess. :munch:
     
  13. SableSal

    SableSal SHO-ABLE Owner

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    LOL... I told a fellow co-worker I wanted to race him. He laughed at the SHO which is the reaction I'm used to (w/ the Sable), he mainly laughed cause I had the knock in the engine compartment. I told him it's the 220 horses knocking at the door waiting to be released... he then started busting up laughing.

    I'm heading out to the junk yard this weekend. I'll start taring some SHOs apart and see what I can do as far as the timing goes. I guess I'll have to do the side 60K here instead at my buddies house in Modesto...

    Hamal, thanks for the info. I'd love to do a 3.2 swap. My main focus is being able to autocross this puppy. Suspension and trans mods are in my future. :) BTW, it's been a California car all it's life. I highly doubt it'll have issues with rust, but who knows. I'll keep you informed.

    Thanks everyone for the help! I will post what I find, most likely this weekend!

    Thanks again all!
     
  14. F-22 Raptor SHO

    F-22 Raptor SHO New Member

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    Yes, crank PULLEY. I was typing while distracted....I corrected my post. thank you.
     

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