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Thread: unknown noise

  1. #1
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    Corvette(s)
    1989

    Default unknown noise

    I have an 89, and after it warms up, I get what sounds like a bag of marbles rattling. I think it is coming from my exhaust system. could this be coming form my cat going out. engine seems to run fine and when cold makes no noise at all. I just got the car and am still feeling my way around it only has 43000 miles on itClick image for larger version. 

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  2. #2
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    Corvette(s)
    1984 Two-tone Blue Coupe

    Default Yes, the noisy Cat could be the problem

    Sounds like the Cat is gone.

    It would be fine until it heats up, then noisy...with only low miles on it, time would have killed the Cat



    Tony

  3. #3
    Member Huskerman's Avatar
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    2010 Grand Sport Coupe Z16 Blade Silver

    Default

    Great looking car by the way....I had a 90 of that color.....

  4. #4
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    Default

    Sounds like pre-ignition to me. If it is you would have the noise when you step on the gas or put a load on the engine, but not at idle. Is that what's happening? What octane gas are you using? A octane rating of 89 is required at the least. On the passenger side of the engine below the plugs is a knock sensor. It looks like a engine temp sensor. Check the wiring and the sensor. The knock sensor will retard the timing if it hears a knock and is working right. If low octane gas is used or the timing is set to high and the knock sensor is bad, you'll have that sound. Check your timing and the sensor first, its an easy fix if thats the problem. The octane of the gas used, can be boosted with an additive untill you run the tank down and fill it with 89 octane. If you hear that sound at idle, it could be lifters. That would be more of a ticking sound tho. As far as the cats being bad and rattling with the low mileage is beyond my thinking. I've never came across that happening in my experiences, but thats not to say its unlikely. Does your check engine light come on? Have you checked to see if any codes have been set? If your timing, gas and the sensor and wiring check out Ok, then look else where. I think what I suggested is the place to start and eliminate that first. Others may have different opinions than mine, so take it all into consideration. One thing I was wondering about at the last minute here, was to ask if you had engine run on after turning the key off. That would if it does that, lead me to think I'm right. Noise is sometimes hard to track down, because it can travel, good luck and I hope this helps you. Be sure to let us know what you find and what it was. Bill

  5. #5
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    Default

    I just noticed you had a problem with opening the hood on another post. If you get it open, and adjusted so it doesn't happen again....great! If not, there's a trick I use to make it easier than fooling around with that tool. Get some small diameter aircraft cable and some pinch rings. Put the cable alongside the release cable attachment point where the orignal cable connects and put a pinch ring on it just like the orignal is attached. Run the other end thru a small hole which you'll have to make thru the gasket leading it to the wiper arm. Keep it as straight as possible, then form a loop using a pinch ring. Keep it just long enough to lay nicely hidden, but easy to grab when the hood is closed. If you have that problem again, or the orignal cable breaks, just reach down by the wiper arm and give that cable a pull. If done right, its out of sight, cheaper than the tool, and saves time fooling around with it. Takes only minutes to do! By the way, nice looking car! I have an '89 Vert, triple black and looks like new also. Great car, fun to drive, but a sink hole for money....lol...Good Luck with it!.....Bill

  6. #6
    Tuna's Avatar
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    '13 427 60th

    Default

    Quote Originally Posted by mlm0 View Post
    I have an 89, and after it warms up, I get what sounds like a bag of marbles rattling. I think it is coming from my exhaust system. could this be coming form my cat going out. engine seems to run fine and when cold makes no noise at all. I just got the car and am still feeling my way around it only has 43000 miles on it
    I had a similar issue with my old '92 years ago. Turned out to be the Cats.

    I noticed it most when I was in a drive through with the windows down and the engine idling. Told my service adviser that it sounded like a bunch of rocks in a tin can (bag of marbles). Had a small shop gut the Cats and put them back on and never heard the sound again. Of course I live in a state that doesn't have inspections so no one really cared that the Cats didn't work.
    Tuna
    NCM Lifer - NCM Fighter Squadron
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  7. #7
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    Default

    I think I have it nailed down to one of the pulleys driven by belt. now just have to find out which one.

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