Mystery klanking sound.. over 200K N*
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Northstar Engines and System Technical Discussion Discussion, Mystery klanking sound.. over 200K N* in Cadillac Engine Technical Discussion; Okay, here goes. My 95 Eldorado has a klanking sound coming from (possibly) the bottom end. I had a complete ...
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    eldoradoin's Avatar
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    Mystery klanking sound.. over 200K N*

    Okay, here goes. My 95 Eldorado has a klanking sound coming from (possibly) the bottom end. I had a complete bottom end rebuild at 150K. It "klanks" along with the starter, and at idle speed (around 750 rpms). The engine sounds perfect at or above 900 rpms). Newer transmission, flexplate and torque converter. ( I checked them all, no play) My question.. what the hell is it? It sounds like someone banging two oil cans together (for those who remember oil cans). I thought the bottom end of the N* was bulletproof.

    The only code I'm pulling is a P132 -knock sensor circutry. I don't think a bad knock sensor would even cause this noise.

    Anyhow, any ideas? Would a bad belt tensioner make this noise? Belt driven accessories?


    As always.. thanks for the input ahead of time.

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    Ranger's Avatar
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    Re: Mystery klanking sound.. over 200K N*

    What do you mean by "klanks along with the starter"? Have you checked for a broken starter pinion return spring? Maybe the pinion is bouncing off the flywheel ring gear.

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    Re: Mystery klanking sound.. over 200K N*

    Hey Ranger.. sorry, forgot to say that I replaced the starter too. That would be too easy, now wouldn't it?

    edit: Now, you have an idea of the "klanking" sound I'm talking about though. It would sound like the starter pinion stuck out and banging off the flex plate.

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    daveyhouse is offline Cadillac Owners Fanatic
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    Re: Mystery klanking sound.. over 200K N*

    possibly a hairline crack in flywheel? Borrowed a truck that had the noise you are describing last year. The flywheel had no play but we dropped the tranny anyway, and low and behold it had a crack near the mounting bolts. Replaced it and the sound was gone.

    It only did it at an idle or certain unloading conditions, never during acceleration

    Edit: Hopefully it IS your starter pinion.

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    Re: Mystery klanking sound.. over 200K N*

    The flexplate was changed last summer. I'm wondering if anyone has shimmed their starter. I've used shims on other GM vehicle's starters, but they were the exterior type.

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    Re: Mystery klanking sound.. over 200K N*

    Never heard of one needing to be shimmed.

    Try this. Take it for a ride and make a hard right turn. If you hear that clanking, then I'd put money on the pinion returns spring. Centrifugal force would be throwing the pinion into the spinning flywheel ring gear. A hard left would slide it back away from the flywheel.

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    Re: Mystery klanking sound.. over 200K N*

    I thought that it just had to be the starter pinion as well, but what are the chances of two of them having the same problem?

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    Re: Mystery klanking sound.. over 200K N*

    Slim (unless the replacement was a cheap aftermarket AZ Don'tLast starter).

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    Re: Mystery klanking sound.. over 200K N*

    It was a cheap aftermarket starter... 70 bucks on ebay. The sound didn't go away in the first start though. I'm wondering if those goofballs put my flexplate in wrong. I went for more than a year without this noise. I was really listening last night, and the starter might just be the problem.

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    Re: Mystery klanking sound.. over 200K N*

    All bets are off. You're just gonna have to pull the manifold and have a look.

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    Re: Mystery klanking sound.. over 200K N*

    It isn't like I haven't been in there before. Thanks Ranger..

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    carnut is offline Cadillac Owners Master
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    Re: Mystery klanking sound.. over 200K N*

    My money is on a cracked flexplate where it bolts to the crankshaft. Sometimes you can see a rust streak from the bolt on the flexplate face. The crack flexes and rust forms on the crack and streaks down from the bolt hole. The flex plate is a very tight fit on the crankshaft end. If not fully seated when replaced, it would flex too much and crack. Why was the flex plate replaced in the first place?

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    Re: Mystery klanking sound.. over 200K N*

    Quote Originally Posted by carnut View Post
    My money is on a cracked flexplate where it bolts to the crankshaft. Sometimes you can see a rust streak from the bolt on the flexplate face. The crack flexes and rust forms on the crack and streaks down from the bolt hole. The flex plate is a very tight fit on the crankshaft end. If not fully seated when replaced, it would flex too much and crack. Why was the flex plate replaced in the first place?
    The flexplate was switched out, after 214,000 miles. It centered out, so I don't think it's the problem. One question for all. How many portals are there to check the crank/flexplate. I'm thinking a wrench is in there. seriously.. :/

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    carnut is offline Cadillac Owners Master
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    Re: Mystery klanking sound.. over 200K N*

    What is centered out?

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    Manic Mechanic is offline Cadillac Owners Fanatic
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    Re: Mystery klanking sound.. over 200K N*

    Have you checked the Harmonic Damper? It's common, esp. at your mileage. Pull the LH front wheel and liner to expose it and look for defunct elastomer between the hub and pulley. If you can just look down at it and see anything or it wobbles you've found it already.

    Vernon
    eldoradoin and eldoradoin like this.

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