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Old 08-26-2014, 09:15 PM   #1
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Engine knock on startup

2011 Automatic Sport DD 51000 miles

I have noticed for a while that on cold starts my 3.8 makes a quick slapping sound for about 2 seconds. Sounds like a dry engine though oil is fine. I use full Synthetic religiously every 5000. I use whatever is on sale at Advance Auto. I typically upgrade to the K&N filter. Current oil is Kentrol. Today when starting for first time in 24 hours the engine made a loud single thump along with the slapping noise.

My searches reveal that this is considered normal. Noise like this tells me that metal is touching metal. How can this be normal? Has anyone else out there experienced this and now are dealing with engine problems as it ages? should I be concerned?

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Old 08-26-2014, 10:14 PM   #2
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It could be the anti drain back valve in your filter is bad. It happens. Try a new oil filter, and pre-fill it as much as possible before installing it. Some engines make start up noise from time to time.

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Old 08-26-2014, 10:17 PM   #3
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Prob not the same thing but my 2012 does this on occasion. Rare and no rhyme or reason to it as far as I can tell.

Edit: just the quick rattle. Haven't had it thump yet.
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Old 08-26-2014, 10:26 PM   #4
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Quote:
Originally Posted by demarpaint View Post
It could be the anti drain back valve in your filter is bad. It happens. Try a new oil filter, and pre-fill it as much as possible before installing it. Some engines make start up noise from time to time.
I have to admit I've never filled the filter with oil when changing the oil. Just read about that recently. Although I dont get it - I assumed it would fill once I started the motor. What is the mechanical advantage to pre filling?
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Old 08-26-2014, 10:36 PM   #5
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Originally Posted by GeePStrings View Post
I have to admit I've never filled the filter with oil when changing the oil. Just read about that recently. Although I dont get it - I assumed it would fill once I started the motor. What is the mechanical advantage to pre filling?
You're correct the filter will fill itself. However pre-filling helps to get the oil flowing faster to the engine internals, reducing start-up wear after an oil change. People like myself that are a little OCD prefer to fill the filters, IMO it helps. Some filters hold close to a qt of oil, and pre-filling helps quite a bit, if the filter is situated in a position that allows for pre-filling it.

A bad Anti Drain Back Valve can cause dry starts each time the engine is shut down and left for a few hours. A bad ADBV will allow the oil to drain back into the engine, and you'll sometimes hear start up noise, because the filter has very little oil in it.

The 2012 is a totally different animal, has the filter on the top of the engine and no ADBV.
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Old 08-27-2014, 12:44 AM   #6
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Quote:
Originally Posted by demarpaint View Post
You're correct the filter will fill itself. However pre-filling helps to get the oil flowing faster to the engine internals, reducing start-up wear after an oil change. People like myself that are a little OCD prefer to fill the filters, IMO it helps. Some filters hold close to a qt of oil, and pre-filling helps quite a bit, if the filter is situated in a position that allows for pre-filling it.

A bad Anti Drain Back Valve can cause dry starts each time the engine is shut down and left for a few hours. A bad ADBV will allow the oil to drain back into the engine, and you'll sometimes hear start up noise, because the filter has very little oil in it.

The 2012 is a totally different animal, has the filter on the top of the engine and no ADBV.
^^^This

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