LC9 5.3 knock noise and check oil coming on

Andy Manager Cambridge, Nebraska Posted   Latest  

Guys I have a 2009 Chevy Silverado k1500. I took truck on a long trip and on the way home the engine started slightly knocking and the oil pressure would drop along with a message check engine oil. Oil level was ok. Started engine after sitting awhile and the oil pressure was around half. Check engine light with a P0521 EOP sensor performance and P0522 EOP sensor circuit low. I replaced the oil pressure sending unit and screen also tested wiring (wiring test ok with very little resistance and not open) cleared codes, oil pressure good but knock is still there cold and hot. So took engine apart found a intake lifter on #4 cylinder with a flat spot and #4 piston scored. My question is what are these marks in the cylinder wall? Why did engine oil pressure drop to almost 0 psi on dash? Would the oil pressure drop cause the scored piston? The rod and main bearing look o.k. also. Thanks in advance for any help.

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Nathan Owner/Technician
Hillsboro, Ohio
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Following. I'm in the process of swapping an lc9. Dealership checked it out said it needed a motor. The customer complaint was similar. Except for no complaint on oil pressure. I remember doing an oil pump on a 5.3 about that year. There was a TSB stating something about oil pump failure. I purchased an oil pressure test kit that tested at the oil filter. Makes verifying oil pressure pretty…

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Josh Service Manager
Greensboro, North Carolina
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Nathan, checking oil pressure at the filter housing verifies the pump is working. We always connect two gauges, one at the filter housing and one on the VLOM where the oil sender is located to see if they are the same. If pressure is lower on the top, then you have bearing clearance or spun bearing issues with the top end.

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Andy Manager
Cambridge, Nebraska
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Sorry guys forgot to mention that after checking the wiring also checked oil pressure at the sending unit and the oil filter before changing the sending unit. The top end pressure was 32 psi and the bottom was at 36 to 38 psi hot at idle (only warmed up in shop to operating temp.) This variance I thought was pretty close due to gauge variations. I was wondering if the vlom could leak enough oil…

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Victor Owner/Technician
Doral, Florida
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In second that motion(washdown)

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Josh Service Manager
Greensboro, North Carolina
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Hi Andy. It's hard to know for sure if I'm seeing on the picture exactly what you see in person. The light can do weird things to images when you are trying to see details like cross hatch pattern in a photo... Having said that, the image looks like cylinder walls no longer have the cross hatch pattern all the way around the cylinder and their may even be some grooves deep enough to snag a…

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Ethan Educator
Rapid City, South Dakota
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Second that about cam bearings causing oil pressure issue.

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Andy Manager
Cambridge, Nebraska
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I will pull the cam and see if I can identify a spun cam bearing. Is there anything to pay close attention to if everything looks good?

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David Mechanic
Stockport, United Kingdom
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Hi Andy , did the engine over heat at the time or at any time in the past because that piston looks like it seized in the bore . And the cooling jacket look dirty was the coolant rusty ? Regards and good luck with it Dave . PS does the con rod have a jet to spray oil onto the cylinder bore if so is it clear and place ?

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Randy Diagnostician
Glendora, California
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Dido over heating problem

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Andy Manager
Cambridge, Nebraska
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David The engine has never over heated. Not sure on the connecting rod jet I will check. Thank you.

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Mike Technician
Salina, Kansas
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From the pictures looks like lack of oil because the cylinder hole to the left looks the same marks , like others posted could have the cam bearing on #4 spun heated up and then locked back in place . Has the engine been ran low on oil , changed out when it should have been , over heated pulling a heavy load ? Thank you

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Victor Owner/Technician
Doral, Florida
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My take is lack of cylinder lubrication caused by washdown​.​You need to take a good look at injector on that cylinder.

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Andy Manager
Cambridge, Nebraska
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I like the way you are thinking. Take a look at the post and question I made to Josh. I will also have the injector. Thank you

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Eric Owner/Technician
Edgerton, Wisconsin
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It looks like you have the same marks in the cylinder next to the one pictured. I've seen marks like that from liquid in the cylinder discoloring the cylinder. Coolant, water, something was in the cylinder and caused the stain. It looks like the block still has the cross-hatches in the cylinders, have you checked the cylinders for wear? I think the same thing that caused the stain on the…

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Michael Mobile Technician
Clinton, Utah
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Looking at the piston skirt I have to wonder about the oil change frequency and type of oil used. How many miles are on the vehicle. Does it have DOD? (Long lifters that shut off at times) Did you buy it new or used? Are you running E85? With lots of Alcohol in the fuel, it runs more fuel through the engine. Lots of short runs allows the fuel to dilute the oil giving less protection. Just some…

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David Mechanic
Stockport, United Kingdom
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Just had a thought Andy did the oil pressure relief valve stick open ? Regards Dave....

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