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help! - loud clanging rattle under car at speed

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Old 12-11-12, 04:27 PM   #1
LScowboyLS
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Default help! - loud clanging rattle under car at speed

when I am on the Interstate, say at 70mph, I get like a random clanging banging noise under the car - but I pulled over and all parts of the exhaust system seem in great shape and the car runs and handles great.

my theory is that perhaps some gravel may have gotten up inside a heat shield in the exhaust system and the high speed wind in causing turbulence and rattling these rocks around - does that sound likely? - other theories?

how many heat shields are there that I need to disassemble and check? - anyone had this happen before?
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Old 12-11-12, 05:55 PM   #2
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There is alot of shielding under these cars. Could be anywhere. Does the sound change with rpm?
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Old 12-11-12, 06:44 PM   #3
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Does your have the main lower engine cover still on? Any cracks on it and especially around where the mount bolts go?

There are also two side covers where the strut mounts are, check those. The rest of the covers don't get as much turbulent air as the front ones do. Otherwise some suspension bushing is definitely unhappy at that rate of speed so there is metal on metal contact. If you drive over a rough surfaced road at lower speeds does it occur?
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Old 12-11-12, 07:50 PM   #4
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I never keep my main engine cover on, it seems!

and the noise seems to be coming from the underside of the car, at least halfway or all the way to the back, like at the rear wheels area - I see some shields near the tires that would be the right place.
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Old 12-12-12, 04:21 PM   #5
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ECU discussion goes in that thread. It has been a hot discussion and helpful. Any differing thoughts do it in PM or let it go. We want to be helpful for each other here.
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Last edited by RA40; 12-12-12 at 04:25 PM.. Reason: Re-wording.
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Old 12-12-12, 05:27 PM   #6
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Put the car in the air and smack the shielding with your hand. A broken weld on a shield on the exhaust itself can chase a resonance at a certain speed....
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400ls, 96, back, car, faster, is250, is300, lexus, loud, louder, noise, rattle, rattles, running, speed, underneath

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