Califokie

The LS engines ( 4.8 and 5.3L) have had different issues what erratic oil press gauge readings.. If the engine sounds normal but the gauge reads low or sometimes even high the problem is probably a clogged screen that is under the Oil Pressure Sensor located on the left top of the bellhousing behind the Intake Manifold... This is a common failure and most people have at least heard about it..

Now with that being said, A customer left his 04 GMC Sierra with a 5.3L T code ( 8th digit of VIN) engine out in front of my shop the night before for me to change that screen to see if it would correct his oil pressure issues.. Well, I knew as soon as I started it the next morning and it rattle at me for about 5 seconds and then pumped the oil pressure up to about 30 to 35 psi as I pulled it into my shop, that this was NOT a dirty screen issue... The truck had 210K miles on it and the owner was ready to just call it wore out and find another truck.. The truck had been serviced regularly it's entire life and now here it was with low oil pressure issues, so he asked for my advice about if the truck was worth fixing.. My answer was ABSOLUTELY... In my opinion the LS motors are some of the very best engines on the road. Just like it's SBC predecessors, the engines are right next to being bullet proof..

This low oil pressure issue was caused by a weak design that was made when the engineers actually made the oil filter housing part of the oil pan.. The oil literally has to go through the oil pan gasket and oil pan to get to the filter.. The oil pan gasket has two O-rings built into it that seals the inlet and outlet to the oil filter. This design allows an o-ring to split and allow oil to escape the lubrication system and dump right back into the oil pan leaving no visible outside trace of an oil leak.. So a failed oil pan gasket can make you think that your engine is wore out... Another weak spot in the engine is another o-ring used on the pickup tube where it seals to the oil pump that hardens and allows oil to escape back into the pan there also..

To fix the truck I pulled the 4 bolts and dropped the crossmember, removed the oil pan, drilled out the rivets used to secure the oil pan gasket to the oil pan at the factory, pulled the pickup tube and replaced the o-ring on it and put the oil pan back on with a new gasket.. The truck now maintains 45-60 psi oil pressure and no longer rattles when starting up cold... Due to the fact that the oil pan bolts need to be torqued in sequence to prevent alignment problems I strongly suggest not doing this yourself.. However it is about a 4 hour job that is much cheaper than buying a new engine or truck.

geo1

Informative post,thanks

Rednucleus

Filing in my memory banks; thank you!
What year motors does this apply to?

Califokie

I only mentioned the 4.8 and the 5.3 because those are the only ones I've gone into for it.. They were all early to mid 2000s with over 100K miles.. They were in GMC Sierra, Yukon, Tahoe, C and K 1500 pickups.. These are just the ones that I have personally done and saw major improvements. I believe that all LS motors ( including the 6.0) were designed this way.. I guess it just takes awhile for the problem to show up... It's first sign is the oil pump losing it's prime from sitting for awhile ( like over night) and allowing the engine to rattle a second or two until the prime is pumped back up. That part is usually the o-ring on the pickup tube hardened.. After warming up you might notice a little lifter noise accompanied with a lower than normal oil pressure reading ( that's the oil pan gasket coming into play). The ones that I saw the most were 5.3 L both the T code ( 8th digit of VIN) and Z codes ( the flex fuel) engines ( which is probably because they are the most popular).. With that design I cannot see any LS motor not developing this problem eventually, but do not let this deter you from owning one because I still believe that they are the best engines on the road.

ajparry89

Bringing this one back. I am working on an 09 5.3L. do you think this could be a problem on this late motor as well, or did they resolve anything by then? I got low oil pressure gauge readings, and oil pressure sensor code. pulled the sensor to replace it and the screen. old screen did not look real clogged up at all, but none the less replaced it anyway. didnt fix the issue. i sit under 20lbs at idle, maybe 10-15. no noises upon start up, everything sounds find at all times. just the low readings. any other suggestions?

Califokie

It is very possible ... I've done several LS's this way ( replacing pan gasket and o-ring on the pickup tube) and only one was not helped by it ( it had actually been ran low on oil).. The oil pressure loss takes place when the o-ring that is built into the pan gasket splits and allows oil being pumped into or out of the oil filter to escape through the gasket and back into the oil pan ( no outside sign of leaking is very possible), the result is a constant low oil pressure reading because the higher the oil pressure gets the more it escapes back into the pan... The O ring at the top of the pickup tube where it seals to the oil pump also hardens and allows a loss of the vacuum that pulls oil into the oil pump causing lower pressure because of less oil quantity in the pump.. The latter condition usually lessens as the engine warms up because the O ring softens from the heat but when it cracks it is a constant condition just like the pan gasket issue... 2010 was the latest model that I have personally done but I just imagine that all LS's can develope this problem... I did this to a 07 Tahoe that was rattling so bad that this was a last resort before buying another engine, it left running quiet and maintained 45 lbs of oil pressure ( it came in with about 15) .
.

ajparry89

Cool thank you for the reply. I am currently working on this job this weekend and got the parts here already. they dont have many known issues with their oil pumps?

ajparry89

I just got mine removed. the o ring around the pickup tube seemed fine. not broken, and still bendable and pliable and somewhat soft. i could fold it without it breaking/cracking. however on the oil pan gasket, which is metal with rubber and rivetted to the pan, has the two ports above the oil filter housing area. and one of the rubber seals was half separated from the metal portion of the gasket. it was resting in place, but separated. could that be the culprit? at this point I just hope so haha.

ajparry89

UPDATE: I did this repair, and then used 10w30. seems to be working fine now! Thanks everybody!

94burb

Although this may be the case for many, it was not for me on my 5.3 with approx 150k at the time. Not much of a startup knock but rather a hot idle of under 10 psi triggering the engine light.

I tried:
replacing the sensor a few times
replacing the screen, then removing the sensor screen all together (original was spotless)
replacing the pick up tube o ring
replacing the oil pressure relief valve
replacing pan gasket a few times
FINAL F'YOU FIX... Hi Flow Hi Pressure oil pump... 60 psi Max and 20psi min with 10w-40 summers/10w-30 winters

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Present : 2007 Suburban LTZ 200k with "AFM Delete" set-up: MORE POWER... SAME FUEL MILEAGE!
Past:1994 Suburban LT, 2001 suburban LT