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metalic rattle at startup

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Old Sep 14, 2009 | 04:47 PM
  #1  
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Default metalic rattle at startup

When I start my 2008 c6 I hear a metalic rattle coming from just behind the front tires near the rear of the engine.
I suspect that it is exhaust related since it stops approx. 10 seconds after the car is started. I only notice it in the morning during cold start up.
Any idea what this noise could be?
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Old Sep 14, 2009 | 05:38 PM
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It's probably the lifters pumping up. It's normal and nothing to worry about.
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Old Sep 14, 2009 | 07:02 PM
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Nope, not lifters. the sound is like shaking a coffee can with shards of metal in it. Very noticable, and loud. The lifters do make a slight noise at startup, but not this noise.
Thanks for your suggestion.
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Old Sep 14, 2009 | 08:39 PM
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Originally Posted by nomo50
Nope, not lifters. the sound is like shaking a coffee can with shards of metal in it. Very noticable, and loud. The lifters do make a slight noise at startup, but not this noise.
Thanks for your suggestion.
Mine makes this noise also, when the ac is off on a cold start its not as loud.
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Old Sep 15, 2009 | 09:39 AM
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Could it be some sort of heat shield that stops rattling after heating up?
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Old Sep 15, 2009 | 12:31 PM
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One possible cause of this is what I call rod rattle. It will only happen when car has been sitting for a while.

The oil filter check valve (the rubber diaphram under outer holes of filter) is not sealing and allows oil to drain out of intake line to filter. So upon initial start up you experience the rattle from lack of oil pressure creating the hydro-dynamic wedge of oil that help reduce metal to metal contact (which is what you maybe hearing).

Change your filter and check it before purchasing by (this sounds odd) blowing into large center hole, if you do not hear or feel air escaping from smaller intake holes filter is good to go. If its a leaker, back in box and check another.

This may or may not be the cause of your noise but is has worked for me and sounds like what you maybe encountering.

SR
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Old Sep 15, 2009 | 05:57 PM
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Originally Posted by Stage Runner
One possible cause of this is what I call rod rattle. It will only happen when car has been sitting for a while.

The oil filter check valve (the rubber diaphram under outer holes of filter) is not sealing and allows oil to drain out of intake line to filter. So upon initial start up you experience the rattle from lack of oil pressure creating the hydro-dynamic wedge of oil that help reduce metal to metal contact (which is what you maybe hearing).

Change your filter and check it before purchasing by (this sounds odd) blowing into large center hole, if you do not hear or feel air escaping from smaller intake holes filter is good to go. If its a leaker, back in box and check another.

This may or may not be the cause of your noise but is has worked for me and sounds like what you maybe encountering.

SR
I understand what your saying. That might be it, but its high pitch just like and exhaust shield rattle.
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Old Sep 15, 2009 | 06:46 PM
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sounds like an lsx series engine... Mine does that out of the blue sometimes.
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Old Sep 15, 2009 | 09:02 PM
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Can also be your catalytic converter.
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Old Sep 15, 2009 | 10:31 PM
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Check the center exhaust support retaining clips.
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Old Sep 15, 2009 | 10:45 PM
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Originally Posted by nomo50
Could it be some sort of heat shield that stops rattling after heating up?
You think it heats up in 10 seconds ??? That engine must be like a Blow Torch My bet it is a heat shield near the Catalytic converter... or exhaust related...
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Old Sep 16, 2009 | 02:03 AM
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I had one of my exhaust cans hitting the sheild above them and it made that sound. I also have had an exhuast clamp hitting one of the shields by the x pipe too that made that sound. Check there before you start getting crazy.
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Old Sep 16, 2009 | 04:07 PM
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Do you have NPP exhaust?
If you do, it could be the butterflies chattering as they close.
Mine does a similar noise and I've narrowed it down to the butterflies.
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Old Sep 21, 2009 | 01:29 PM
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OK, Here's the story.
I got under the car this weekend. The noise is coming from the x pipe.
If I hit the x pipe with my hand, I can hear the rattle. It is internal to the pipe. Any idea how to resolve this except remove the x pipe and see what the cause is?
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Old Sep 21, 2009 | 05:13 PM
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Originally Posted by nomo50
OK, Here's the story.
I got under the car this weekend. The noise is coming from the x pipe.
If I hit the x pipe with my hand, I can hear the rattle. It is internal to the pipe. Any idea how to resolve this except remove the x pipe and see what the cause is?
Did you check the center retaining clips as I said in post #10. That is the problem I had that drove me crazy. One was simply out of adjustment after the x-pipe was installed.
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Old Sep 22, 2009 | 06:21 PM
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Originally Posted by nomo50
When I start my 2008 c6 I hear a metalic rattle coming from just behind the front tires near the rear of the engine.
I suspect that it is exhaust related since it stops approx. 10 seconds after the car is started. I only notice it in the morning during cold start up.
Any idea what this noise could be?

Have a 2008 same here for a few second probably the exhaust. Only happens in the morning with me forget it its nothing. Leave it alone or your 10 second problem can go full time.
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Old Mar 27, 2012 | 09:07 AM
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I know this is an old post, but I have started the same exact problem. What was done here to fix this issue?
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