Not the normal oil pressure issue

[maddss99]

07 Suburban, 215k, AFM delete kit installed with new Oil Pump (Mellon M365), new Oil Pressure Switch, oil screen removed, new O-ring and a L92 Valley Cover.

 

So when the truck is cold the oil pressure is about 55psi, once the truck reached normal operating temp, the oil pressure drops to just below 20psi.  It stays about 20psi when the truck it at idle or just above when at 2000 RPM.  I do not hear any ticking sound when the truck is cold.   It throws a code of P0251.

 

Possible problems

1.  O-ring may have been installed incorrectly,

2.  Oil sending unit might be bad

3.  Oil relief valve in the pan might be stuck.

 

Any help would be great.    

 

[jackmac]

Did you find your problem? I have one doing the same thing. Thanks 

[redvett]

20 psi at idle is plenty actually at 1000 rpm's it should be around 7 psi.

[jfath14]

On 5/9/2018 at 10:58 PM, maddss99 said:

07 Suburban, 215k, AFM delete kit installed with new Oil Pump (Mellon M365), new Oil Pressure Switch, oil screen removed, new O-ring and a L92 Valley Cover.

 

So when the truck is cold the oil pressure is about 55psi, once the truck reached normal operating temp, the oil pressure drops to just below 20psi.  It stays about 20psi when the truck it at idle or just above when at 2000 RPM.  I do not hear any ticking sound when the truck is cold.   It throws a code of P0251.

 

Possible problems

1.  O-ring may have been installed incorrectly,

2.  Oil sending unit might be bad

3.  Oil relief valve in the pan might be stuck.

 

Any help would be great.    

 

Honestly man, if you do not hear the ticking on the driver side you are in good shape. My 1500 (2012) has always struggled with "low psi" at idle, around 20 psi, and I have not had any issues. Now, my 5.3, like many 5.3s does eat oil but that tick is a dead give away when it needs more. I have had experience with the sending unit and replacing it. Unless your oil pressure is dropping to zero that is likely NOT the problem so you can take that out. Which is a good thing for you because that wiring harness gives such little slack that getting the new sending unit installed is a pain in the butt. I am curious, just check your oil and see if it has the full 6 to 6.5 liters in there. 

[jfath14]

On 10/10/2020 at 1:25 PM, jackmac said:

Did you find your problem? I have one doing the same thing. Thanks 

What steps have you gone through to diagnose your issues? Maybe I can help. 

[redvett]

P0251 does not apply to a gas engine only a Diesel.

[jackmac]

41 minutes ago, jfath14 said:

What steps have you gone through to diagnose your issues? Maybe I can help. 

Thanks for the reply jfath14,  I have checked with a manual gauge at the port on the front of the block ,cold start it will read 45 psi and slowly start dropping to  around 11 psi hot, gauge will respond quickly when engine rpm goes up. 1000 rpm it will raise to about 20psi when hot. Now with the manual  gauge on the sending unit location 28psi cold and slowly drops to   5-6 psi hot and barley hits 10 psi at a 1000 rpm. No engine noise .   The strange thing is literally the day before it done this I had 40 psi cold 28-30 hot but would go to 40 again at 1000 rpm. overnight it changed. I have done a VLOM mod where I block the oil passage to the solenoids and cut the tower gaskets and turned off the AFM with a HP tuner. I have done this same mod at least 20 times and never had a oil pressure issue so I'm thinking it is just coincidence it happened after the mod. ??  Could the pick up tube O ring do this or the AFM pressure valve in the oil pan? Thanks for any insight you have.

[jfath14]

1 hour ago, jackmac said:

Thanks for the reply jfath14,  I have checked with a manual gauge at the port on the front of the block ,cold start it will read 45 psi and slowly start dropping to  around 11 psi hot, gauge will respond quickly when engine rpm goes up. 1000 rpm it will raise to about 20psi when hot. Now with the manual  gauge on the sending unit location 28psi cold and slowly drops to   5-6 psi hot and barley hits 10 psi at a 1000 rpm. No engine noise .   The strange thing is literally the day before it done this I had 40 psi cold 28-30 hot but would go to 40 again at 1000 rpm. overnight it changed. I have done a VLOM mod where I block the oil passage to the solenoids and cut the tower gaskets and turned off the AFM with a HP tuner. I have done this same mod at least 20 times and never had a oil pressure issue so I'm thinking it is just coincidence it happened after the mod. ??  Could the pick up tube O ring do this or the AFM pressure valve in the oil pan? Thanks for any insight you have.

What is the exact model of your GM? 

[jfath14]

2 hours ago, redvett said:

P0251 does not apply to a gas engine only a Diesel.

I saw that and thought that was an odd code so I just left it alone. Maybe a typo. 

[jackmac]

3 hours ago, jfath14 said:

What is the exact model of your GM? 

2008 Silverado 5.3  vin 0 

[jfath14]

What oil filter are you using? I ask because I had a mobile1 for a while and over time and the pressure was dropping gradually. I switched to a fram and it corrected the problem immediately. It sounds stupid and I was skeptical at first but it made a difference. Do you have any leakage around your oil coolant lines? (Inside driver side front wheel under the block) That is a common place for some oil loss and compression issues. I would also urge you to check how much actual oil you have in the engine. That engine really does devour oil the older it gets and anyone who tells you anything else has just gotten lucky with the engine they received. ESPECIALLY if they still have the AFM active. That 5.3 will burn oil every single time it switches from V4 to V8.