HELP!!! Motor knock! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-03-2011, 12:49 AM   #1
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Default HELP!!! Motor knock!

I have a 2006 GMC sierra, 4 door, 4.8l, 2 wheel drive with 104,000 miles. Just recently after a 270 mile trip it developed a "knock" or tick in the motor. It was an all-of-the sudden noise, just went outside, cranked it up and there she went. The knock follows the rpms, it speeds up with the motor, but doesn't get louder and actually seems to go away when the rpms are around the 3000 range. I've always changed the oil between 3000 to 4000 miles and the truck has great oil pressure and runs as smooth as ever. Pulley noise has been eliminated as I've taken the belt off and cranked it up and it was still there. I've never driven the truck hard and have always taken good care of it. Any suggestions would be awesome. Thanks!
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Old 10-03-2011, 07:39 AM   #2
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Old 10-03-2011, 08:53 AM   #3
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Moved to GMC
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Old 10-03-2011, 09:27 AM   #4
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It is important to know if the knock or tick is coming from the top of the engine or the bottom. A ticking noise could be a bad lifter in the top end, and a knock could be piston slap or a bearing problem in the bottom. Use a mechanics stethoscope ($10 - $12 at a parts store) or a wood dowel to listen to various points on the engine to see if you can narrow down where the noise is coming from.
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Old 10-09-2011, 10:00 PM   #5
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Ok, I've ran some seafoam through it twice and still same noise. We've determined that it is coming from the top of the engine just past the valve cover on the driver side. Any suggestions?
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Old 10-12-2011, 02:04 PM   #6
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almost sounds like a loose TC or a collapsed lifter
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Old 10-12-2011, 06:07 PM   #7
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Here are some links to videos of the engine. Check it out and see what you think. As for the collapsed lifter, that'* what I thought the whole time but I've had three mechanics tell me it wasn't but that really doesn't mean anything.

IDLE:

THROTTLING:
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Old 10-12-2011, 06:17 PM   #8
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To me it sounds like something is rubbing. Have you removed the belt? If not, do that and start the engine. But don't run it for long, you will have no water moving. That will at least rule out pulleys, water pump and alt.
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Old 10-12-2011, 06:33 PM   #9
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Yes I did remove the belt and run it, same noise.
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Old 10-12-2011, 06:47 PM   #10
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It just sounds like something is rubbing and squeaking.
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