Chevy S-10 thumping


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Old 12-02-06, 10:08 AM
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Chevy S-10 thumping

I have a '95 Chevy S-10 with an unusual, regular thumping sound (about once a second or so). It sounds as if someone is tapping on the inner fenderwell. It only starts after the engine is hot, usually after driving for 10-15 min, and engine is at or near idle. (i.e. After coming to a stoplight.) Once the engine is shut off, the thumping continues for 15-20 seconds and slowly fades. It is noticable both inside and outside the vehicle, and seems to be loudest around the thermostat. (The thermostat has been replaced and made no difference.) Due to a separate problem, the radiator, water pump, and radiator cap have also been replaced with no effect on the thumping noise.
 
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Old 12-02-06, 12:09 PM
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Is your radiator fan loose and hitting the shroud?
 
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Old 12-02-06, 12:43 PM
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Originally Posted by HotinOKC
Is your radiator fan loose and hitting the shroud?
Nope, but that's almost what it sounds like. It continues after the engine is stopped (fan is clutched- driven off the serpentine belt), sometimes for as much as half a minute, and it doesn't do it cold or on short runs, only after it's been driven a while.
 
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Old 12-02-06, 03:53 PM
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Check your exhaust. Sometimes brackets bust and the exhaust will bounce back and forth.
 
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Old 12-03-06, 12:11 AM
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Nope, doesn't seem to be exhaust (I know that sound- had a van that did it). At first I thought it was air trapped in cooling system, but now after replacing most of it due to a separate problem it doesn't seem to be. Only thing left that I know of that would keep doing it after the engine is stopped would be a vacuum component, but I can't trace the noise. I was hoping someone had a similar problem, and have searched the archives here with no result. <scratches head>
 
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Old 12-05-06, 08:00 PM
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Update:
The knocking seems less intense since it has gotten colder, so I'm pretty sure it's heat related.
 
 

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