2010 LC9 Low Oil Pressure fixed by oil filter

[Black02Silverado]

A UOA will definitely tell you if the oil is thinning due to fuel dilution.  This is a baffling situation for sure.  Running a thicker oil will not hurt anything to see how it effects this.

[newdude]

On 3/26/2021 at 11:40 AM, Bethard728 said:

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

 

 

Have you verified oil pressure with a mechanical gauge at the filter and at the sensor end?  

 

Amazon.com: Kent Moore Tool EN-47971 Oil Pressure Gauge Adapter for Generation 4 & 5 V8 Engines (Blue): Automotive  This is the oil filter pressure test adapter.  

 

Amazon.com: ICT Billet LS Engine Swap M16 1.5 Adapter to 1/8 NPT Oil Pressure Sensor LS1 LM7 LR4 LQ4 LS6 L59 LQ9 LM4 L33 LS2 LH6 L92 L76 LY2 LY5 LY6 LC9 LFA LH8 LMG LS3 L98 L9H L20 L94 LZ1 L99 L96 LC8 L77 551172: Automotive    This should get you at the sensor side.

 

Amazon.com : oil pressure tester

 

Check it cold and hot, but I'd be more interested in hot pressure.  

 

Do you consume any oil at all?  In addition to an oil analysis, I would check for any oil consumption after 1000 miles on a fresh filter and fresh oil.  Don't check it in between the 1000 miles either.  When you do check it, get it hot then let it sit for 30 minutes on level ground to allow for proper drain back to the pan then check it.  

 

When you changed the AFM pressure relief valve in the pan, did you add the relief valve deflector shield if it wasn't already there?  

 

On 3/27/2021 at 8:18 PM, swathdiver said:

  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.

 

8 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?

 

PF-47 will not even screw on the Gen 4 LS engines.  PF-48, PF-48E, UPF-48R are all correct filters for Gen 4 LS.  Some have substituted with a PF-63.  GM prefers the use of the PF-48E.  

[Bethard728]

7 hours ago, Grumpy Bear said:

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

Can you help me understand how this tells me it’s the oil?   I leave the oil in and change the filter, then it’s good for another 1500 miles.   This seems to me that the filter is the issue.  Wouldn’t it mean the oil is the issue if I changed the Oil only?  

[Bethard728]

5 hours ago, newdude said:

 

 

Have you verified oil pressure with a mechanical gauge at the filter and at the sensor end?  

 

Amazon.com: Kent Moore Tool EN-47971 Oil Pressure Gauge Adapter for Generation 4 & 5 V8 Engines (Blue): Automotive  This is the oil filter pressure test adapter.  

 

Amazon.com: ICT Billet LS Engine Swap M16 1.5 Adapter to 1/8 NPT Oil Pressure Sensor LS1 LM7 LR4 LQ4 LS6 L59 LQ9 LM4 L33 LS2 LH6 L92 L76 LY2 LY5 LY6 LC9 LFA LH8 LMG LS3 L98 L9H L20 L94 LZ1 L99 L96 LC8 L77 551172: Automotive    This should get you at the sensor side.

 

Amazon.com : oil pressure tester

 

Check it cold and hot, but I'd be more interested in hot pressure.  

 

Do you consume any oil at all?  In addition to an oil analysis, I would check for any oil consumption after 1000 miles on a fresh filter and fresh oil.  Don't check it in between the 1000 miles either.  When you do check it, get it hot then let it sit for 30 minutes on level ground to allow for proper drain back to the pan then check it.  

 

When you changed the AFM pressure relief valve in the pan, did you add the relief valve deflector shield if it wasn't already there?  

 

 

 

PF-47 will not even screw on the Gen 4 LS engines.  PF-48, PF-48E, UPF-48R are all correct filters for Gen 4 LS.  Some have substituted with a PF-63.  GM prefers the use of the PF-48E.  

Sorry!   I misspoke on the 47 in my original post.    It was the 48E that I tried.  It does not consume any measureable amount of oil.  I did add the deflector when I changed the relief valve.  I have checked with a actual gauge at the sender and my gauge isn’t lying.  I really am losing pressure.   I have not checked at the filter port.   

[Grumpy Bear]

8 hours ago, Bethard728 said:

Can you help me understand how this tells me it’s the oil?   I leave the oil in and change the filter, then it’s good for another 1500 miles.   This seems to me that the filter is the issue.  Wouldn’t it mean the oil is the issue if I changed the Oil only?  

You said it looses no pressure until 1500 miles then it does. 

I asked if you had tried changing the filter only and you said multiple times and it makes no difference. Looses no pressure until 1500 miles then it does. 

 

Ergo it is NOT the filter if changing the filter has zero effect. 

 

Look. I had a UOA at around 90,000 miles that showed 2.4% fuel dilution and with it the 40C viscosity was one grade lower and the 100 C viscosity right at minimum spec. I couldn't smell it and you sure can't see it. Test the oil at 1500 miles. Viscosity reduction can cause pressure loss. Why I said a *W40 might slow it down. But test the oil FIRST to verify. This is a process not a dart board you hit a bullseye on if you aim well. 

 

The only difference other that a bit of size between the PF43 and PF63E is the relief valve setting. The 43 has a 12 psi spring and the 63E has a 22 psi spring. But that will have zero influence on measured oil pressure. None. 

 

I got nothing more on this topic. 

Edited March 30, 2021 by Grumpy Bear

[newdude]

8 hours ago, Bethard728 said:

Sorry!   I misspoke on the 47 in my original post.    It was the 48E that I tried.  It does not consume any measureable amount of oil.  I did add the deflector when I changed the relief valve.  I have checked with a actual gauge at the sender and my gauge isn’t lying.  I really am losing pressure.   I have not checked at the filter port.   

 

Have you done a pressure test with a filter adapter like I posted to see the pressure without the oil filter in the picture?  Or was your test up top at the sensor hole?  

[swathdiver]

On 3/26/2021 at 11:40 AM, Bethard728 said:

...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.

 

Well, it's time to have the oil analyzed, time to send off a sample to Blackstone Labs for analysis.

[Bethard728]

48 minutes ago, swathdiver said:

 

Well, it's time to have the oil analyzed, time to send off a sample to Blackstone Labs for analysis.

Thanks for everyone's suggestions!!  I truly appreciate the time you have all spent trying to help.  I also want to apologize for some of my confusing posts.  I obviously was not clear on any of my posts that changing the filter ONLY "fixed" my pressure issue for awhile.   I'm just going to yank the motor out and see what I can find.  I came here hoping to find someone that has fixed this problem or find someone that has had an LS apart to see if the "barbell" failure can dump oil back in the pan.   I have read about this a lot and everything I find dead-ends without a fix.  I just cant see how it can be the oil when changing JUST the filter cures the problem for another 1500 miles or so.  I literally go from 40+ psi at a hot idle with a fresh filter on the SAME oil that had ZERO pressure the same day....and it holds the pressure the same amount of time as fresh oil.  I would have a very high mixture of fuel dilution to completely knock my pressure out.  Hell, I actually ran a 302 on straight diesel fuel once to clean out sludge on a neglected motor and it carried some oil pressure.  I know they are very different engines, but I just cant buy that my oil is diluted enough to kill pressure and not even raise the level by a fraction of a hair.  I don't mean to come here and be rude or ungrateful, because I know everyone's time is valuable and I really do appreciate the suggestions.

[Bethard728]

1 hour ago, newdude said:

 

Have you done a pressure test with a filter adapter like I posted to see the pressure without the oil filter in the picture?  Or was your test up top at the sensor hole?  

I tested the pressure at the top.  I will try to find the adaptor to test it at the pump.

[swathdiver]

Keep us posted Jeff.  I lose a few psi between clean and dirty oil but after near 40 years of driving and wrenching on cars have not come across your situation.

[newdude]

1 hour ago, Bethard728 said:

I tested the pressure at the top.  I will try to find the adaptor to test it at the pump.

 

I'd be most curious to see what you find out.  If its dropping off down at the filter test, I'd be suspect maybe of an oil pressure issue in the pump when its warm?  

[Bethard728]

18 hours ago, newdude said:

 

 

Have you verified oil pressure with a mechanical gauge at the filter and at the sensor end?  

 

Amazon.com: Kent Moore Tool EN-47971 Oil Pressure Gauge Adapter for Generation 4 & 5 V8 Engines (Blue): Automotive  This is the oil filter pressure test adapter.  

 

Amazon.com: ICT Billet LS Engine Swap M16 1.5 Adapter to 1/8 NPT Oil Pressure Sensor LS1 LM7 LR4 LQ4 LS6 L59 LQ9 LM4 L33 LS2 LH6 L92 L76 LY2 LY5 LY6 LC9 LFA LH8 LMG LS3 L98 L9H L20 L94 LZ1 L99 L96 LC8 L77 551172: Automotive    This should get you at the sensor side.

 

Amazon.com : oil pressure tester

 

Check it cold and hot, but I'd be more interested in hot pressure.  

 

Do you consume any oil at all?  In addition to an oil analysis, I would check for any oil consumption after 1000 miles on a fresh filter and fresh oil.  Don't check it in between the 1000 miles either.  When you do check it, get it hot then let it sit for 30 minutes on level ground to allow for proper drain back to the pan then check it.  

 

When you changed the AFM pressure relief valve in the pan, did you add the relief valve deflector shield if it wasn't already there?  

 

 

 

PF-47 will not even screw on the Gen 4 LS engines.  PF-48, PF-48E, UPF-48R are all correct filters for Gen 4 LS.  Some have substituted with a PF-63.  GM prefers the use of the PF-48E.  

Thanks for the links Enthuisiast!  I ordered the pressure testing kit because I had just been using a manual gauge that I happened to have an adapter to fit the sending unit hole.  I will test it at the filter next time it drops pressure.  Then I will at least know if its an issue before the filter or after.

[KAQ]

Hey did you figure this out. Mines doing the same thing driving me nuts

[Bethard728]

11 hours ago, KAQ said:

Hey did you figure this out. Mines doing the same thing driving me nuts

I can't say that I have made any progress for certain because I haven't driven the truck much.  I dropped the transmission out to check the barbell (I swapped in a billet one) and did a rear main seal why I was there.  The barbell was fine, so that was not my issue.  I have talked with at least 6 people that had this problem too and never figured it out, they just ended up getting rid of the truck or replacing the engine.  I actually talked to a GM mechanic that says he has seen engines with all new bearing still do it after the rebuild.  Currently, I am running a cheap filter and it is doing fine, but I have not paid attention to how many miles I have driven since the last filter change.  I did not waste my time with an oil analysis because it's obviously not oil dilution because changing the FILTER ONLY solves my problem for awhile.  For now my plan is to drive it until it causes major issues and then rebuild it or swap in a reman.  (I would just rebuild but I'm worried after talking to the GM tech that has seen new bearing not solve the problem)  The more I have researched, the more I have found this is an extremely common issue and it is odd that nobody has solved the problem....maybe someday LOL

[Grumpy Bear]

On 3/30/2021 at 8:23 AM, Bethard728 said:

 I just cant see how it can be the oil when changing JUST the filter cures the problem for another 1500 miles or so. 

 

Well that's more clear or perhaps it just fell on me. Who knows. Anyway. 

 

2012 GM moved the pressure regulation from the pump discharge to main galley. You have a 2010 so regulated at the pump if I have my ducks squared up. That would indicate the filter is plugging. I'd cut open a failed filter.