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Discussion Starter #1
So I started up a thread a long time ago on this issue, and I got back into researching it. So my 2008 Ls with 73k still rattles on startup, for about 2 seconds. The longer it sits, the longer it lasts. It seems I've found it could be two things. Either the timing chain tensioner, or oil draining back out of the filter (because I guess our cars' filters don't have drainback valves?), and thus the engine is running dry for a few seconds. Don't know much about mechanics, but this seems to be what I've learned. If it's the timing chain tensioner, is it bad, does it need to cleaned, or do I just need to use a thicker oil or something? If it's the filter, are there any good filters that might stop this problem? Perhaps ones that DO have some kind of drainback valve? I've seen a few threads on this topic, but no real answers on how it got fixed. It seems that everyone has bad luck with dealers. Any thoughts? Thanks!
 

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I thought the noise on startup was normal for an ecotec. my car does it, my brothers, both of my friends cars that have cobalts as well.
 

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It's normal if you have the first tensioner design but doesn't mean it is desirable or any good for the guides or chain. The second design has a better engineered check valve and keeps it's prime much, much longer.
 

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so the new design doesn't make the rattle sound at all?
 

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After a couple of weeks of not being started it might but not for and over night stop.
 

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Discussion Starter #7
Pretty sure it's the timing chain tensioner. Check if it has a bump on the head bolt if not I would get the revised version of the tensioner.



---------- Post added at 07:03 PM ---------- Previous post was at 06:58 PM ----------

I beieve this is the one.

Acdelco OE Service 12608580 Timing Damper Timing Chain Tensioner | eBay

Cool, thanks! Now, I have to pull the valve cover off just to see the tensioner right? If I do need to replace it, should I just follow CED's instructions? (www.crateenginedepot.com/pdfs/12608580INS.pdf). Or is it basically bolt it back in and call it a day? CED makes it sound more intensive than I thought.

---------- Post added at 10:31 PM ---------- Previous post was at 10:30 PM ----------

And I heard you don't need to 'load' the new style or anything? That seemed like a finicky process...
 

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Pull your valve cover, zip tie the chain a few times on each sprocket. Take out old tensioner, put in new tensioner

Sent from AutoGuide.com Free App

---------- Post added at 10:14 PM ---------- Previous post was at 10:13 PM ----------

Tensioner is located on the back of the head closest to front cover. Its a 1 1/4 inch socket. The oil filter cap socket is perfect

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