Knocking - Vid
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Instructor
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From: Calgary
Knocking - Vid
Hey I was hoping someone could shed some light on my issue im dealing with my C5. (97 100km-60k miles)
Knocking doesn't go away when engine has warmed up, no power loss issues, temp and pressure all normal. Not sure if its lifter or piston slap? or something I haven't even thought about
Thanks
http://www.youtube.com/watch?v=7_uiCVRHMxk
Knocking doesn't go away when engine has warmed up, no power loss issues, temp and pressure all normal. Not sure if its lifter or piston slap? or something I haven't even thought about
Thanks
http://www.youtube.com/watch?v=7_uiCVRHMxk
Last edited by Limp Noodle; Aug 11, 2009 at 12:17 AM.
Advanced
Joined: Oct 2008
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From: Nova Scotia
I agree with Blown 346 that it's probably valvetrain related. Fairly 'high frequency' (thin?) tapping sound as opposed to a bottom end knock.
It's also possible that you have an exhaust manifold/port leak. These can present themselves as a surprisingly sharp metallic tapping sound. Try using a (2' long or so) piece of garden hose...one end to your ear and one for probing engine. This will help locate the source. Of course, be real careful not to get wound up in any moving belts etc.
It's also possible that you have an exhaust manifold/port leak. These can present themselves as a surprisingly sharp metallic tapping sound. Try using a (2' long or so) piece of garden hose...one end to your ear and one for probing engine. This will help locate the source. Of course, be real careful not to get wound up in any moving belts etc.
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Sounds like valvetrain to me too. Definitely NOT rotating assemble (i.e. spun bearing) knock. Loose rocker, bent pushrod, worst case scenario would probably be a dead lifter.
Tech Contributor
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From: Dyer, IN
Additionally, I would isolate to a bank, and pull the valve cover to inspect for a cracked valve spring....or lost needle bearings in a rocker.
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I listened to it here on a laptop so the sound resolution isn't so great. With that understanding, it sounds like a cylinder is pushing compression past a head gasket. I agree with those above too in that the valve train needs to be examined right away. Could be a valve not quite closing. A cylinder leak down test will show that. A compression test will do the rest.
Team Owner
Joined: Jan 2004
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From: NJ
First thing I would do is check for an arcing plug wire. Sometimes a plug wire can come loose and arc to the plug in such a way that it still fires. This is unlikely but worth a shot.
The next step would be to pull that valve covers and cover the points already mentioned above. It sounds like an issue with the valve train, maybe a bad rocker or lifter.
The next step would be to pull that valve covers and cover the points already mentioned above. It sounds like an issue with the valve train, maybe a bad rocker or lifter.
Drifting
Joined: Feb 2006
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From: Boston MA
That sound reminds me of the knocking I was getting last month. Turns out that one of the spark plugs wasn't tight and it was slowly backing itself out of the head. The knocking was coming from the wire boot hitting the headers. Just a thought, but it may not be that easy for you.
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Very little actually but use some shop rags just to make sure nothing drips on the exhaust.
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It also sounds like an exhaust leak. If you rev the engine and let it coast down,,,does the noise go away?? If so, thats an exhaust leak.
Could also be a valve train issue. You can remove the valva cover and there will be very little oil. The gasket is an O ring and reuseable.
Check rockers for puked roller bearings bent pushrods.
BC
Could also be a valve train issue. You can remove the valva cover and there will be very little oil. The gasket is an O ring and reuseable.
Check rockers for puked roller bearings bent pushrods.
BC
Last edited by Bill Curlee; Aug 11, 2009 at 11:51 PM.
Drifting
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From: Arlington Texas, originally from San Angelo, TX
