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~2011 CTS-V Coupe & 2013 SRX~
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Discussion Starter #1
Hi,

Since i got my "V" (2004 w/13,010m.) Every cold start-up of the engine i hear a "gurgling knock" coming out of it until it warms up.... at that point it disappears. At first, i was thinking pulley tensioner, or air pump, but i do not think that noise from them would go away after the engine warms up. After researching many post, piston slap seemed identical to my problem.

The same postings seem to claim that piston slap was an issue with pre-2003 engines, and that GM re-designed the engines pistons after that. Is their anything else that could cause a "gurglly knock" when cold, then go away when hot, or could i be one of the lucky few that have the piston-slap issue?
 

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How's all you fluid levels? I have a little over 7K on my 04. No slapping. A bit of valvetrain tapping at startup.
 

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'04V, '05V, '06SRT8, '10V, '13ZL1, '12 V, '16 Z06 SC757
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27,000 miles here and no slap. I do however have a 2002 Tahoe with 61,000 miles and significant slap. Sounds like a washing machine at start up.
 

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crushing Vs with my Wurm
2013 GT500 - 700+ HP
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dont think it pertains to our LS6 does it? (at least the website...?) More likely lifters getting pumped up from their nightly sleep.

F
 

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Stangar said:
Checkout www.pistonslap.com They have plenty of recordings already.
Interesting, that audio sounds like wrist pins to me. Piston slap has more of a dull thud or knock (lower note) what you hear is the piston changing direction. Sounds like coconut shells.:yup:
I find that the LS-6 has a little knock on start up mostly when its very cold as these hypereutectic pistons shrink.
Aluminum grows and shrinks quite a bit. If you want to hear real knock, get some forged pistons, they are quite noisy..

From GM on the new engines
"This piston knock anomaly that has been occurring in some ’97-’01 engines after start-ups in cold weather is not a durability concern. It’s a pleasability issue on which there was enough input from customers that GM made a production change. Like the revised rings, there’s no performance advantage in switching to the tighter clearance and the polymer-coated piston. Those hearing a cold piston knock are better off ignoring it until the engine warms a little, rather than subjecting themselves to the stress of a dialog with a GM dealer intended to force repair or replacement of the engine."
 

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lasstss said:
Those hearing a cold piston knock are better off ignoring it until the engine warms a little, rather than subjecting themselves to the stress of a dialog with a GM dealer intended to force repair or replacement of the engine."
That attitude alone displays why GM is in the situation they're in.

WTF?? Wait until the engine warms up and ignore it rather than "subject" yourself to a dialog with a GM dealer intending to force repair or replacement of the engine.

That is some sad, and at the same time, funny sheet.
 

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2002; 25K miles, but first noticed it maybe 8K ago; never got around to taking it to the dealer, and now it is off warranty. I only heard it when cold, so I am not too concerned about it
 

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2009 Z06 / 2013 F150 EcoBeast / 2008 Twin-Turbo Bimmer
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To combat cold engine noise, GM has the PCM setup to remove between zero and fourteen degrees (load, rpm and ECT dependent) of ignition timing until the engine coolant temp reaches 176 *F.

It's possible one could make this cold engine noise strategy more aggressive to reduce the noise.

What brand/octane of fuel are you running? Under what rpm/load conditions is the noise most pronounced? At what engine coolant/oil temps does it go away?
 

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~2011 CTS-V Coupe & 2013 SRX~
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Discussion Starter #20 (Edited)
When i first got the car (recently)..... It had a 1/4 tank gas in it.... Every time i shut it off it "lightly dieseled". I put in octane booster and filled it up with 93 octane. So that is where i am now. Strange thing, i still get a chug or two after i shut it off. Noise is at idle. I'll have to watch the temperature and report back.
 
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