2005 engine knock
Thread Starter
Pro
Joined: Aug 2009
Posts: 517
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From: Westchester NY
2005 engine knock
I recently heard an engine knock on my c6. I'm getting a little stressed cause I think it may be a rod knock. I was hoping it was a lifter or a rocker but I don't think I am that lucky. The car is a 2005 m6 with headers intake pulley and tune. It has 25k miles. Here is a quick video. Any ideas?
Melting Slicks
Joined: Jun 2004
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Racer
Joined: Aug 2008
Posts: 497
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From: Garner NC
Rod knock and throwing a rod are two different things when it comes to the level of damage. It might also be a wrist pin. If the pressure is still good and you haven't run it much, you may be in luck. If it's a rod bearing sometimes you can replace the offending bearing and be back in business. No promises, but if it runs perfectly otherwise significant damage may not have set in. I'd pull the pan and take a look, if nothing else to at least know what you're dealing with.
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Thread Starter
Pro
Joined: Aug 2009
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From: Westchester NY
The knock does not go away at all. It's there from initial start up till it's completely warm. The 35 is fully hot, it may be a little higher but the pressure never drops low. If I pull the pan I will be able to see all the bearings? What does a destroyed one look like?
Race Director
Joined: Oct 1999
Posts: 13,298
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From: Somers NY
Nope 
the car was at the track the week before & ran 11.6x 4 times with no problem..
We put on a new FAST intake manifold & wanted to get some HP #'s .. that was the 2nd run ..
On the first run it made 407 HP.. on that run...
the car was at the track the week before & ran 11.6x 4 times with no problem..We put on a new FAST intake manifold & wanted to get some HP #'s .. that was the 2nd run ..
On the first run it made 407 HP.. on that run...
Thread Starter
Pro
Joined: Aug 2009
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From: Westchester NY
I drained the oil, it had about 300 miles on that change and it looked clean. The magnet on the end of the drain plug didn't have any metal on it either. Still made the sound with fresh oil in it too. Thinking about selling the car cause I don't want to pull the motor at all.
Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
I drained the oil, it had about 300 miles on that change and it looked clean. The magnet on the end of the drain plug didn't have any metal on it either. Still made the sound with fresh oil in it too. Thinking about selling the car cause I don't want to pull the motor at all.
If that solves the knock then you have a worn bearing someplace, probably a rod or main.
Racer
Joined: Aug 2008
Posts: 497
Likes: 21
From: Garner NC
You won't be able to really see the bearings unless you pull everything apart, but if a rod bearing is bad the rod will likely have some slop in it, which is the knocking you hear. Usually you can tug on them and tell. Prior to that haljensen is right, some of those oil treatment products (lucas is a good one) may tell you. That stuff is so thick that dumping some in will quiet a bad bearing at least temporarily.
Race Director
Joined: Feb 1999
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From: Indianapolis IN
He is talking about making the oil thicker, so 50w + any thick additive should do the trick, your oil pressure will climb as well.
I have replaced crank and rod bearings from the bottom of the car on my 85, but I don't recommend it and the LS2 is new to me so I do not know if it is even possible
EDIT, one last thing to try is to take the serpentine belt off and start the car, if the sound is there, its the engine and not an accessory. Its worth a try but don't let it run for too long with the belt off.
I have replaced crank and rod bearings from the bottom of the car on my 85, but I don't recommend it and the LS2 is new to me so I do not know if it is even possible
EDIT, one last thing to try is to take the serpentine belt off and start the car, if the sound is there, its the engine and not an accessory. Its worth a try but don't let it run for too long with the belt off.
Last edited by LD85; Aug 23, 2013 at 07:31 AM.
Pro
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I've had that same noise before, unfortunately I can't tell you which of the remedies solved the problem but I had lifters and cam changed because one was stuck, and exhaust manifold gasket when switching to an LS7 exhaust system. A lot of people don't think to check the exhaust manifold gasket but it can produce a noise like that. I noticed mine did anytime after running it hard through the gears.