Engine Bay clunking - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-16-2005, 09:03 PM   #1
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Default Engine Bay clunking

I started up my car tonight, and as soon as I started it, there was a noticeable rattling under the hood. so I popped it, and the rattling sounded like it was coming from underneath the alternator. It sounded like a stick inside a pipe being beat off the inside. The engine seems to run fine, but it sounded like a connecting rod going ***** nilly inside the cylinder. Gearheads, for the love of god, please tell it'* nothing of that sort, and i'm just being paranoid!
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Old 04-16-2005, 09:22 PM   #2
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Check your harmonic balancer. The rubber backing (dampener portion) may be cracked. Watch it carefully while idling. It might be obvious.
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Old 04-16-2005, 11:32 PM   #3
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If you find nothing wrong after a visual inspection remove the drive belt and crank the car. If the noise goes away your problem is minor like a bad PS pump.
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Old 04-17-2005, 02:33 AM   #4
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Well, I gave it a once over in the parking lot, and nothing seemed out of order. The clunking was intermittant, and slowed down after idling for a few minutes.

Ron, the PS issue would make sense, since i have a leak somewhere in that system.
Will, where is the harmonic balancer? I unfortunately haven't learned my way around my car like I need to yet (key word is yet )
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Old 04-17-2005, 02:53 AM   #5
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Guys, could this be a belt tensioner going really bad? Mine are making a little noise and I'm replacing that lovely plastic for metal soon to be safer.
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Old 04-17-2005, 03:32 AM   #6
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I checked the belt, and it didn't seem to be any tighter or looser than it usually is.
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Old 04-17-2005, 03:38 AM   #7
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Sorry..I meant the bearings and spring or tensioning mechanism. Might seem fine sitting there or if you release it. Like every other wear item...they go bad over time.

There is a possibility that it'* your noise. That would be why your engine isn't acting up. Just noisy
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Old 04-17-2005, 04:21 AM   #8
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Quote:
Originally Posted by Puddy46
Well, I gave it a once over in the parking lot, and nothing seemed out of order. The clunking was intermittant, and slowed down after idling for a few minutes.

Ron, the PS issue would make sense, since i have a leak somewhere in that system.
Will, where is the harmonic balancer? I unfortunately haven't learned my way around my car like I need to yet (key word is yet )

The Harmonic Balencer is right behind the crank pulley...more or less part of it I guess. But yeah, what the crank pulley.
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Old 04-17-2005, 12:10 PM   #9
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Quote:
Originally Posted by ron350
If you find nothing wrong after a visual inspection remove the drive belt and crank the car. If the noise goes away your problem is minor like a bad PS pump.
Ron is right. Remove the serpentine belt, start the car, look and listen. If the car runs quietly, the problem is not internal, but with one of the things that is no longer moving, - that is, the water pump, ps pump, the tensioner assembly, the alternator, an idler pulley, or the A/C compressor. As Will pointed out, the only other probability is the harmonic balancer. If it is causing the noise, it may quiet down when you remove the loads imposed by the belt. The harmonic balancer is the heavy assembly on the front of the cranshaft that that balances the flywheel and torque converter on the other end. It is on the bottom cenerline of the engine and has a big pulley attached to it with a rubber coupling. When that rubber joint goes bad, the pulley wobbles and rattles as it tries to drive all of the accessories on the front of the engine. Because it is heavy, when it goes bad, it can produce a low clunking or clanking sound like you described. Don't run the car for more than a minute or so without the belt! You have NO cooling for the engine, without it.
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Old 04-17-2005, 02:06 PM   #10
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Thanks to Hans here is a link to a picture of a L36 that lets you see every thing on the front of the motor.

http://www.bonnevilleclub.com/forum/...316&highlight=



Woops the Bonny in the picture looked newer than a 93.
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