OK, Now what??? Need suggestions on mystery sound.
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Cadillac Seville / Cadillac Eldorado Forum Discussion, OK, Now what??? Need suggestions on mystery sound. in Past Cadillac Vehicle Discussion; 2002 STS, 53,000 MILES, no codes. OK, changed the W/P tensioner pulley. Sound still there. Again, it's kind of a ...
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    Caddydrummer67's Avatar
    Caddydrummer67 is offline Cadillac Owners Fanatic
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    OK, Now what??? Need suggestions on mystery sound.

    2002 STS, 53,000 MILES, no codes.
    OK, changed the W/P tensioner pulley. Sound still there. Again, it's kind of a rattling, rustling, ticking sound with a granular quality, but it's pretty subtle. Only noticeable when your on the gas and the engine is under load. Seems to be coming right from right in front of the driver in the engine compartment where the W/P pulley is. Maybe the W/P itself. That would make sense. Seems to be working fine though. Do they have a tendency to make such a noise before they go?
    I'm starting to think if not the W/P, it may have to do with air intake, but it sure sounds like a bad bearing or something. kind of sounds like a loose timing chain, but coming from the wrong side and that is highly unlikely on a 53,000 mile car. Won't do it when you rev the engine in neutral. Something rattling in the throttle body maybe. But if that was it, why would it not make the sound in neutral? Tranny??, shifts fine, runs great, will make the sound in every gear. Can't think of any reason the tranny would make this noise. Cracked flexplate?, pretty extreme, and unikely on a low mileage car and the sound is too subtle and doesn't seem to be getting any worse. I'll have to take the intake system apart next, been meaning to clean the TB and get a buttplug anyway.
    Any ideas?, is there something else I need to consider? I know this sound sould not be there.

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: OK, Now what??? Need suggestions on mystery sound.

    WPs generally leak when they start to go bad, but rarely at your mileage. Flex plate was the thought that came to mind as I read your post, but that also would be rather premature.

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    turbol15 is offline Cadillac Owners Enthusiast
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    Re: OK, Now what??? Need suggestions on mystery sound.

    maybe engine pinging. usually under load

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    Caddydrummer67's Avatar
    Caddydrummer67 is offline Cadillac Owners Fanatic
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    Re: OK, Now what??? Need suggestions on mystery sound.

    Cracked flex plate would be pretty extreme. If that is what it is, I would expect it to get noticeably worse. I've put about 3000 miles on since I noticed the sound and it does not seem worse.
    Pinging?, I don't think it's running hot, and I'm running premium fuel. I suppose if the timing wasn't right, like over-advanced, that could cause pinging. Or perhaps a bad EGR? I've never had a NS do this.
    What is an easy way to rule out pinging? Wouldn't I get some codes if this was happening?

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: OK, Now what??? Need suggestions on mystery sound.

    You will never hear it ping (knock). The knock sensor will detect it long before you can ever hear it and retard the timing to prevent it. If the knock sensor failed, you'd have an SES light and a DTC for it.

    Again, it's kind of a rattling, rustling, ticking sound with a granular quality
    Motor mount or exhaust system maybe?

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: OK, Now what??? Need suggestions on mystery sound.

    No way to alter timing advance in our engines - absolute max is 35 degrees BTDC and that drops back instantly on any sort of acceleration. Even running the recommended 87 octane you'll never hear "pinging" - ignition controls and the knock sensor take care of that (no, you don't lose any "power" when all this is going on).

    You might get some noises from the odd fuel mixtures caused by a sluggish EGR, but that would probably set mixture codes/SES light. The EGR isn't difficult to clean on the 2000+ Northstar. It's the vertical can just right (rearward) of the throttlebody.

    Leaking 4-bolt flange in the exhaust Y > cat connector ?

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