Oil sludge

2011 CHEVROLET SILVERADO
79,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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CHUCK326
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Do I need to change the piston rings, when engine has oil sludge? Can I flush the engine oil?
Aug 26, 2018 at 1:50 PM
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ASEMASTER6371
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Good afternoon.

You can try and use sea foam for the oil system.

Add it to the oil and run the engine at idle for one hour. Change the oil and filter. You may have to do it several times to get it all out depending on the amount of sludge.

As far as the rings, does it burn oil?

Roy
Aug 26, 2018 at 3:20 PM
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CHUCK326
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No it does not, and it will start and run.
Aug 26, 2018 at 3:21 PM
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STEVE W.
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It depends on how bad the sludge is. If it is very thick and lots of it I would go through everything on the engine to clean it out. The old trick to clear out sludge was to run the engine until it was warm, then drop the oil out and refill with a 50/50 blend of oil and diesel fuel or ATF. Then run it a few minutes to circulate the mix, shut it off and let it soak. Start it back up, let it warm up and drain out the crud. Then drop the oil pan to clean it and the oil pump screen. Replace the filter and add oil, run it to flush out the rest and change the oil and filter again. However on a 2011 I am not sure I would do that unless it was a last attempt on a high mileage engine. With the tighter clearances and passages it would be easy to flush a chunk into the wrong place and cause oil starvation. Instead I would pull the rocker covers and manually remove as much as possible there and remove the pan and do the same. Then do oil and filter changes and add a half quart of ATF to the oil. Then change the oil in five hundred miles or so and run it. You could strip it all down, clean it all out and go from there but that is a lot of work that may not be needed.
Aug 26, 2018 at 3:28 PM
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CHUCK326
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Thanks Steve, I am going to change the cam, timing kit and oil pump. My nephew who was a mechanic at one time said I should replace rings. Sludge is not that thick, 79,000 miles.



Aug 26, 2018 at 3:38 PM
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STEVE W.
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I probably would not as long as it is not burning oil or showing sings of carbon build up on the plugs or valves. Does the cam show wear or did it eat a lifter?
Aug 26, 2018 at 4:59 PM
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CHUCK326
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Not sure, have not looked at it yet. When it runs it misses real bad, analyzer says plug #5. Other people have told me to change cams?
Aug 26, 2018 at 5:08 PM
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STEVE W.
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Any clatter or low compression in that cylinder? Have you changed the plugs, swapped the coil and such? Those are also prone to injectors shorting out.
Aug 26, 2018 at 5:46 PM
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CHUCK326
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New plugs and wires, thought about coil, but it was okay.
Aug 26, 2018 at 5:51 PM
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STEVE W.
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I would check the injector and swap the coil to another cylinder. Would hate to see you open it up for a bad injector.
Aug 28, 2018 at 6:03 AM
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CHUCK326
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Hey Steve, replaced the coil and put new injectors in. Did not miss at first but had no power, after about five miles started missing real bad again. I have also taken a valve cover off to check for sludge, not very much there.
Sep 1, 2018 at 8:36 AM
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STEVE W.
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Do you have a scan tool available? If so get the codes read and post them here. If it ran okay but low power it sounds like a possible short in the harness to the injectors. Take a test light and probe the injector harness using a couple pins to back-probe them. See if there is one or more that is not firing properly. Also, verify that none of the wires got put onto the wrong injector.
Sep 4, 2018 at 1:49 PM