Aluminum 5.3 lost oil pressure thoughts?

[c4mo]

I realize this is maybe not a performance based topic, but thought some of you might have some insight. Lh6 5.3 out of a 08 envoy. Lost oil pressure then came back, at times the oil pressure gauge would sway left and right +-5psi. Thought at first it might be screen and oil pressure sensor so I changed with no effect on problem. Figured then it must be the o ring on the pick up tube drawing air, but when I took the pan off the o ring looks fine. Could this be a lifter issue or a relief valve problem on the pump? Thanks for any help.

[CGT]

Oil pressure relief valve?

[ProPower engines]

X2
They have an aluminum body and steel pressure relief valve. After oil changes crap in the pan gets washed down from the upper engine area when fresh oil is added and the sucked up in the pump thus the relief jams causing low OP.

There use to be a myth about what filter being used made this happen and luberfiner was the only filter to use on them but they make the filters for GM so draw your own conclusions on that issue.

My local dealer sells about 50 pumps a week although not all genuine GM pumps they tell me most are the melling equivelent but they still sell lots of new oil pumps every week.

[BCjohnny]

Not application specific but times three .......

Had various engines over the years exhibit fluctuating pressure and it's usually the PRV, mostly seating of the shuttle valve itself rather than spring pressure.

Had an L18 back in the day have no discernible gauge pressure at idle, swapping out the (external) PRV shuttle restored normal function.

[dannobee]

Your local dealer sells a lot of oil pumps because there's a bulletin on it to replace the oil pump for a sticking oil pressure relief valve.

The bulletin is PIP4158H, doc ID 5392317 if you have access to GM Service Information.

BUT, if the oil pressure light is on on the dash but a mechanical gauge near the engine oil filter shows normal, there's a valve lifter oil filter that can plug up on AFM engines (Your LH6 has AFM). It's under the oil pressure sender at the back of the engine, drivers side, attached to the lifter valley cover, under the intake manifold. Some people confuse this with the engine oil filter. It's not, it's a small screen insert that can be cleaned with brake cleaner.

THAT bulletin is PIP4786C, doc ID 4573569, again, if you have access to GM Service Information.

[A_VAS]

dannobee, he changed that screen/filter that's under the sensor already with no change


I've done that 2x now on my '09 LFA engine...once the gage starts fluctuating I put a new screen in and it's good for another 30k+ or so
I'm guessing at some point the screen won't be the fix, and the pump will need changed....it's at 171k now on the original so could be sooner than later

[ProPower engines]

Your local dealer sells a lot of oil pumps because there's a bulletin on it to replace the oil pump for a sticking oil pressure relief valve.

The bulletin is PIP4158H, doc ID 5392317 if you have access to GM Service Information.

BUT, if the oil pressure light is on on the dash but a mechanical gauge near the engine oil filter shows normal, there's a valve lifter oil filter that can plug up on AFM engines (Your LH6 has AFM). It's under the oil pressure sender at the back of the engine, drivers side, attached to the lifter valley cover, under the intake manifold. Some people confuse this with the engine oil filter. It's not, it's a small screen insert that can be cleaned with brake cleaner.

THAT bulletin is PIP4786C, doc ID 4573569, again, if you have access to GM Service Information.

I am aware but most are not . They do sell pumps but to shops that have the extra details you mentioned.
Most oil change places hate doing oil changes on them here cause the small carbon chunks that develop in the engine get washed down to the PU and jam the pump relief.
Some claimed the wrong filter would do this and there was a couple law suits about that won based on the internet myth about the filtr brand.

[202ci EH]

The relief valve is pre the oil filter so has not much effect, debris and metal from a dead lifter will stick them up.
Not familiar with the pan on that engine but some ls2 and our VE commodore onwards have a second relief valve in the pan.

[CGT]

The mass oil pump failure must be internet based or regional. I along with several friends all work at pretty large GM dealers. Its pretty rare to put an oil pump in one here....at least under warranty anyway. I looked through some history, 1 oil pump in the past 12 months. But we don't see a ton of high mileage stuff so..

Most of the time, from what I have seen. The bypass being stuck in the pump was caused by very high mileage along with very poor maintenance, or one that someone has worked on previously, like doing a cam install etc,,, introducing debris.

I do see a a lot of oil pressure sensor filters, sensors, and oil pressure relief valves(in the pan) though.

[dannobee]

It might have been before your time at the dealership. We were putting them in years ago. Not saying a lot of them, but we did stock them and replace for the low oil pressure complaint.

Look at the PI that I mentioned above, the fact that it's on revision "H" should tell you all that you need to know. It was a known problem over 15 years ago.

[CGT]

Screenshot (1).png

Maybe they revised it to not mention the oil pump? The way I read that document is its not relevant until pre-filter pressure is verified. I've been in a dealer since before the LS came out. I just don't ever recall there being mass oil pump replacing like you hear about on the internet. Who knows. It's not uncommon to see LS stuff come in with low oil pressure that's for sure, they just don't usually get pumps unless someone is shot gunning one, or just trying to sell an engine.

But really by the time you price putting an oil pump, lifters, pressure sensor, relief valve, gaskets and 160.00/hr labor, your usually at the price of an engine and that's what usually happens here.

[dannobee]

Not that bulletin, the OTHER one that I mentioned. PIP4158H, doc ID 5392317

[CGT]

Screenshot (2).png

Not that bulletin, the OTHER one that I mentioned. PIP4158H, doc ID 5392317

Ok I see, so if it fails that test it gets a pump, if it passes...on to the other document.