2007 5.3 Suburban @ 180 k, AFM to NON-AFM repair at 130k

Hi All.... been a while since my last fix... AFM failure. I did a rebuild to a solid non AFM engine with Computer reprogram, basically turned into a 07 hummer engine. About two years later I noticed the oil Slowly creeping to a low oil pressure reading on the gauge. I decided to drop the oil pan and replace the pick up tube o-ring. This repair helped but maybe only for 2 yrs (which brings us to today) and the oil pressure slowly got worse on idle til the point of me asking for help. Runs super strong, even from a standstill with 10psi on the gauge. Still has the noticeable performance boost from the AFM repair, no leaks, no oil burn. I never went below the 1st tic mark (20psi), now i idle at like 10.

The oil pumps design is primarily metal gears.... is this my next potential repair for this issue? I am not familiar with these oil pumps enough to know their failure rate and how to tell if its the actual problem. The screen in the pressure sensor was spot less when doing the AFM repair and actual was just recently remove with a sensor replacement as well but still getting same pressure results.

I have seen many posts on the low oil pressure issue with a handful of solutions... fearing mine may be a worst case scenario.

$$$$ Please toss your two cents at me concerning this topic and any of your own similar scenarios and/or solutions.

 

It's a gear pump with a brass body. If you drop the pan again, replace the oil pump. This also might be a dumb question on my part thinking this is an 07, is the O ring material if you are using synthetic oil, is the O ring viton?

 

Not sure what O-ring material the replacement was but I asked for nothing special other then a part replacement. As far as oil type... I never have put synthetic in this truck.. call me old school I guess. So a gear pump replacement can be done from the oil pan drop? Or best to get at it from the front of the engine?
Brass Body... assuming the Brass is worn?

 

There is a screen under the oil pressure sender that plugs up. Since your not a synth. oil user that is the first and easiest thing to check, pull the sender out and screen is down in the hole below it.

 

I agree, make sure it's not a plugged sending unit. I've never seen a gear pump in a car engine fail. A little bit of wear on a gear pump means alot on the lowering discharge pressure.

 

thanks guys... I mentioned the screen on the main post... it was spotless at 130k and actually not even there now... I left it out when switching the sensor as a test. So currently there is no screen under the oil sensor. I wish it was that easy.

 

What weight oil are you running? My 93 5.7 with 350k is much happier running 20/50 now vs original 5/30

 

That's I would do, change the oil to a higher viscosity before doing anything dramatic.

 

Oil pressure with hot oil is normally 20 on the gauge at idle. Change the sender first, the screen you left out is there to protect the sensor. That's why GM spends the money to put them in there. Verification with a known mech. gauge is the only positive test. And only use a AC Delco sender, parts box store stuff is unreliable crap.
LS motor is a tighter tolerance motor, putting 20-50w in it is 1960's band aid for old worn out small blocks.

 

oil has been changed to 10w-40 since early this yr when i noticed the low pressure again... it has helped for most of the year but no longer. The pick up tube oring job helped a year ago but as of today I hit 10 psi with hot oil at idle. I had also swapped out the ac delco sender unit with the oem one that i saved when doing the AFM removal job. Both oem and acdelco senders give the same results even with out the screen being in place.

What would the oil pressure be when hot if the pump relief valve was stuck open ? wondering if the relief valve is stuck maybe?. What else could be wrong with the pump if anything?