2010 LC9 Low Oil Pressure fixed by oil filter

Bethard728 · March 26, 2021

Hello,

I'm new to this forum and apologize in advance if this is the wrong place. I have searched this forum for days and have not been able to find a solution to my particular problem, but I get an error when I search saying I have to wait " __ seconds until I can search again", so its been a huge challenge to find anything. I have found many people with my problem, but I have tried all the solutions with no success. Anyway, on with my problem. I have a 2010 Silverado 1500 with a 5.3 LC9 AFM. Around 165K miles, I got the oil pressure shut down engine message. After checking the forums, I changed the sending unit and screen under it at the same time I changed the oil. The problem seemed fixed, but after about 1500 miles, it happened again. I changed the oil and it was fixed for another 1500 miles or so. This time, I changed just the filter and, once again, I had pressure for anther 1500 miles. Each time I lost pressure, I could shut the engine off and had oil pressure again after restarting. One day I was about 15 miles from home, pulling about 8K lbs when it happened again. I kept cycling the key, it would get pressure and I would drive a few miles until it happened again. NO engine noise during this whole deal. I made it home and parked it. The next day, I had 45 lbs again when I started it, but about 2 miles down the road, I got a misfire on cylinder 6 along with no compression. So here's where I really struggle to see what is going on.

I opened the motor up and changed all AFM lifters, VLOM, relief valve in pan, cam retainer plate, gaskets, sending unit & screen (again), pick-up tube O-ring and cleaned everything I could get to along with filter/oil change. Everything looked good and the lifter bores where in spec. When I put it back together, everything seemed great until I hit that 1500 mile mark again....and right back to low oil pressure message. So I opened it back up and installed a Melling 10355 oil pump from Summit (with high pressure spring installed) but did NOT change oil & filter. I started the engine and thought my problems were solved for good. I had 60 psi at cold idle. I drove it about 1/2 hour and it held steady at 40 psi hot going down the road. When I stopped next, I get the low oil pressure message again. Same story as before, I change the oil/filter and I have pressure again. I am beyond lost on this truck. The only thing that I have not replaced that I've seen mentioned on forums is the barbell in the oil passage, but I have never read where one fails. Everything I have read pertains to people forgetting them after a rebuild. Other than cam bearings, I cant think of anything else it could be. I am getting ready to pull the engine to dig in, but was hoping I could get an expert that has cured my problem to chime in. I just cant wrap my head around how changing the filter makes it better for 1500 miles or so..... I normally run the good line of filters from Bosch or WiX, but I tried the 48F filter also and it doesn't change anything. I know people have told me to just change the filter every 1500 miles and forget it, but that's not a good solution for me. This will be my 16 yo sons truck and I don't want him taking off to college in a few years dealing with this. Plus, it kinda eliminates any long trips with the rig. Truck has around 186K on it today. Also, I cut open the last filter and it looks normal and fairly clean. I would not call it plugged by an means.

Thanks for any help I can get.

Jeff

swathdiver · March 27, 2021

First, you put the wrong oil pump on your motor, this one pumps at a higher pressure but at 1/3 less volume per revolution. Put the Melling M365 back in.

Have you added an extra two quarts of oil when the pressure drops to see if it goes back up? This is how we test the pick up tube o-rings. I know you mentioned replacing it, new things can go bad. Barring that, my first thoughts reading this post were the cam bearings.

Grumpy Bear · March 27, 2021

Edited March 27, 2021 by Grumpy Bear

Bethard728 · March 27, 2021

14 hours ago, swathdiver said:

First, you put the wrong oil pump on your motor, this one pumps at a higher pressure but at 1/3 less volume per revolution. Put the Melling M365 back in.

Have you added an extra two quarts of oil when the pressure drops to see if it goes back up? This is how we test the pick up tube o-rings. I know you mentioned replacing it, new things can go bad. Barring that, my first thoughts reading this post were the cam bearings.

Thanks for the reply swathdiver. I must of been misinformed from Summit on the oil pump. I was told that the 355 was the correct pump for my truck and had standard pressure and volume unless I changed the spring which would give it standard volume and higher pressure. But either way, I don't see how the factory pump and the Melling 355 would both have pressure for about 1500 miles after an oil change. I have not added extra oil when it happens, but when I replaced the O-ring the first time it was good. I still had pressure issues after the 2nd one was installed, and I replaced it again when I changed out the pump. I am doubtful that all 3 O-ring could all be bad causing pressure loss after 1500 miles on a filter. If you think that is a real possibility I will dump a few quarts in and see what happens.

Bethard728 · March 27, 2021

13 hours ago, Grumpy Bear said:

Thanks for this Gumpy Bear! According to this video, the M355 is the correct pump for my truck. @swathdiver Why do you believe this is the wrong pump?

swathdiver · March 28, 2021

https://www.enginebuildermag.com/wp-content/uploads/Articles/03_01_2012/986163348GMGENI_00000054947.pdf

Just to be sure, download and read this magazine. This is where I got my learnin' from. Unless you were using the wrong o-ring each time, no, I doubt that is the problem. Was it you or someone else that recently put a different oil filter on his truck and cured low oil pressure on this forum? I think he used a PF47, cannot find the post.

Grumpy Bear · March 28, 2021

21 hours ago, swathdiver said:

https://www.enginebuildermag.com/wp-content/uploads/Articles/03_01_2012/986163348GMGENI_00000054947.pdf

Just to be sure, download and read this magazine. This is where I got my learnin' from. Unless you were using the wrong o-ring each time, no, I doubt that is the problem. Was it you or someone else that recently put a different oil filter on his truck and cured low oil pressure on this forum? I think he used a PF47, cannot find the post.

That is an awesome article James. I don't suppose they wrote one for the Gen V yet.

It explains allot about lifter failures without ever saying a thing about it. Bleed down rates and how they changed orientation etc. Very interesting.

Edited March 28, 2021 by Grumpy Bear

swathdiver · March 29, 2021

11 hours ago, Grumpy Bear said:

That is an awesome article James. I don't suppose they wrote one for the Gen V yet.

It explains allot about lifter failures without ever saying a thing about it. Bleed down rates and how they changed orientation etc. Very interesting.

Not aware but if I come across one will let you know.

Bethard728 · March 29, 2021

On 3/27/2021 at 7:18 PM, swathdiver said:

https://www.enginebuildermag.com/wp-content/uploads/Articles/03_01_2012/986163348GMGENI_00000054947.pdf

Just to be sure, download and read this magazine. This is where I got my learnin' from. Unless you were using the wrong o-ring each time, no, I doubt that is the problem. Was it you or someone else that recently put a different oil filter on his truck and cured low oil pressure on this forum? I think he used a PF47, cannot find the post.

Great article! Thanks! I was not the person the cured the problem with the filter...or at least not for very long. You are correct on the PF47 being the filter that people say cures it. I misspoke on my original post. I had no better luck with that filter than I did with the Bosch, it only worked for about 1500 miles. I just cant wrap my head around how this thing has good pressure after the filter change. It will idle around 40 psi hot until about 1000 miles and then gradually starts dropping over the next few hundred miles until it trips the light. Where I struggle is understanding how the filter makes the difference. If my cam bearings are so bad that it has NO oil pressure, how can I have (what I would call great) pressure for so long after a filter change?? The way I understand, oil flow is going from the pump, down the galley to the filter/barbell area and then up to the engine. Its almost like I have an opening between my pump and filter that allows oil to dump back into the pan when the filter starts getting dirty. I have never had the back plate off of an LS to see how the galley is set up, but can anyone tell me if the "barbell" failure could cause oil to dump into the pan if the filter is blocked?

Grumpy Bear · March 29, 2021

2 hours ago, Bethard728 said:

Great article! Thanks! I was not the person the cured the problem with the filter...or at least not for very long. You are correct on the PF47 being the filter that people say cures it. I misspoke on my original post. I had no better luck with that filter than I did with the Bosch, it only worked for about 1500 miles. I just cant wrap my head around how this thing has good pressure after the filter change. It will idle around 40 psi hot until about 1000 miles and then gradually starts dropping over the next few hundred miles until it trips the light. Where I struggle is understanding how the filter makes the difference. If my cam bearings are so bad that it has NO oil pressure, how can I have (what I would call great) pressure for so long after a filter change?? The way I understand, oil flow is going from the pump, down the galley to the filter/barbell area and then up to the engine. Its almost like I have an opening between my pump and filter that allows oil to dump back into the pan when the filter starts getting dirty. I have never had the back plate off of an LS to see how the galley is set up, but can anyone tell me if the "barbell" failure could cause oil to dump into the pan if the filter is blocked?

Perhaps it's not the filter nor the pump but something happening to the oil. Like fuel dilution which will thin it significantly. So will shear thinning. Check injectors for leakage and for weak coils. IF you've already done all that and found them to be in great shape the might I suggest a cylinder leak down test. With 165K on this motor it is possible that a hole or two is getting weak. 1-15% is a great motor. 16 to 25% is okay. 26 to 40% is pretty worn and over 40% is done. If after doing the test you find it is under less than great then you could try a higher SAE grade oil. A thirty of forty something. You can also have a UOA run if all this seems a bit much each 500 miles or so for just fuel dilution and viscosity and plot those. There is an answer you just may be looking in the wrong place. Maybe.

Bethard728 · March 29, 2021

1 hour ago, Grumpy Bear said:

Perhaps it's not the filter nor the pump but something happening to the oil. Like fuel dilution which will thin it significantly. So will shear thinning. Check injectors for leakage and for weak coils. IF you've already done all that and found them to be in great shape the might I suggest a cylinder leak down test. With 165K on this motor it is possible that a hole or two is getting weak. 1-15% is a great motor. 16 to 25% is okay. 26 to 40% is pretty worn and over 40% is done. If after doing the test you find it is under less than great then you could try a higher SAE grade oil. A thirty of forty something. You can also have a UOA run if all this seems a bit much each 500 miles or so for just fuel dilution and viscosity and plot those. There is an answer you just may be looking in the wrong place. Maybe.

I had considered oil dilution, but ruled it out since changing the filter only will bring my pressure back. But maybe its a combination of the diluted oil and dirty filter. I have never checked the injectors for leaks or checked the coils. I assume (maybe falsely) that my coils are good since it doesn't misfire. How would I check the injectors for leakage? The oil isn't noticeably thin or smell like gas and it always stays right on the full mark. I have done a compression test recently, but don't remember exactly what they were at and I lost the paper that I wrote them on. I believe they were all in the 150's. Maybe its worth giving the thicker oil a try when it happens again. I just changed the filter again, so I have great pressure now. I am running Mobil 1 5W30 currently. If I make that change to see what happens, will it hurt to just jump straight to 10W40? I don't drive this truck a lot, so it will be awhile to get the mileage high enough to lose pressure again. Have you ever heard of the barbell coming out on its own? Or do you know if there is a way for oil to dump back into the pan?

Grumpy Bear · March 29, 2021

It takes 15% misfires to 'feel' a misfire. I expect the ECU, however, detects them to a much lower percentage. Should have tossed a code. New Dude, Swathdiver or Cameron could better answer the injector test questions.

One way to separate filter from oil would be next time it looses pressure change only the filter adding just enough oil to restore level. If it's the oil, a filter change will not help. If it's the filter then that motor is trying really hard to clean itself out for whatever reason. I wouldn't have access to it life's history.

Yes 10W40 wouldn't hurt a thing.

Bethard728 · March 29, 2021

16 minutes ago, Grumpy Bear said:

It takes 15% misfires to 'feel' a misfire. I expect the ECU, however, detects them to a much lower percentage. Should have tossed a code. New Dude, Swathdiver or Cameron could better answer the injector test questions.

One way to separate filter from oil would be next time it looses pressure change only the filter adding just enough oil to restore level. If it's the oil, a filter change will not help. If it's the filter then that motor is trying really hard to clean itself out for whatever reason. I wouldn't have access to it life's history.

Yes 10W40 wouldn't hurt a thing.

It hasn't thrown a code since the initial misfire caused by a collapsed AFM lifter. I have done the filter ONLY change 3 different times now. (Each time after ~1500 miles. Then I did filter and oil at 3K) and that fixes the pressure issue for another 1500 miles or so. The engine has always ran synthetic oil changed at 5K or earlier since new. The engine is very clean inside from the top end all the way down to the pickup tube. When I cut open the last filter, it was still fairly clean. Maybe a slight bit of dust looking particles deep in the pleats. The oil has always been clean at 5K miles. I mean its dark, but nothing different from any other vehicle I have had and not sludgy or anything.

Grumpy Bear · March 29, 2021

Okay so that tells you it is the oil and not the filter. Have the oil tested.

garagerog · March 29, 2021

I second Grumpy's suggestion on an UOA. Jeff, to solve your problem may require some thinking out of the box, e.g. have you tried checking your air filter for pinholes with the sunlight test? Have you tried using a synthetic media oil filter? But yes, a used oil analysis has the best odds of pointing you in the right direction.