snives

Gen V L83 5.3, I just finished the engine rebuild and DOD delete and doing the break-in, have 100 miles on it so far. I'm getting low oil pressure warning when the engine is warm and about 4k rpm.
At cold startup I get 37psi at idle, and 39psi at 3.5k rpm. When warmed up I only get 15.4 psi at idle, and 16.8 psi at 4k rpm. It's weird the oil pressure is not raising with rpm. Also weird that its changing so much because of viscosity. This has a variable geometry oil pump driven by a solenoid, it's actually supposed to make too much pressure. . Also of note is I replaced the stock oil galley barbell with the improved racing oil galley barbell, with the o-ring style.

So far I've done the following:
- installed DOD tower plugs (in case the ICT billet dod delete valley cover with seals was leaking)
- installed new oil pressure sensor
- rebuild already had a new cam retainer plate (to avoid problems like this)
- I used the oil pump alignment tool when R&R the oil pump, because I reused the original pump (because it was fine)

Anyone have any ideas? Ever solved this problem before?

strutaeng

Oh dang! Sorry to hear about that.

Tell us why you decided to rebuild it. Was this in a stock application? (Sounds like it if you are getting messages at that low of oil pressure) Or some LS engine swap in some older vehicle?

What about the bearing clearances? That's the most important thing for oil pressures. New bearings? Main, rod and cam bearings? Standard? Was the crank machined any? Polished? Plastigueage at least?

I'm going to guess the bearing clearances were too loose? I'm not sure why the pressure isn't rising with increase in rpm...🤔

snives

I rebuilt the engine because it had a bad lifter that took out the cam. While there I opted for the DOD delete for reliability and also put in a BTR stage 1 turbo cam since that's something for later. Yes, it has new main, rod, and cam bearings. Block was honed, crank was polished and cam bearings were installed at a local machine shop. Standard bearings, clearances were 0.0017-0.0020 on all the rods, mains were 0.0018 - 0.0020, as measured with plastigauge.

strutaeng

Umm. Those clearances look good. Plastigueage isn't exact, but should be be "good enough."

I'm not familiar with with Gen V engines but could that solenoid be the problem? Isn't the engine pump on those engines use that same vane style like the 4L60e? To me it seems like the older geroter style is much better, but this what they are using now, so it doesn't matter what I think really.

What did you do to the oil pump? Were the vanes replaced? I would guess there's a spec on the clearances there as well? How did the housing of the pump look?

snives

The pump is a 12686434, honestly I didn't take it apart or anything so I don't know, but also had no reason to at the time. The way the solenoid works is it changes the geometry of the vane housing, so that it either pumps more volume or less volume. In its failure mode, it defaults to high volume. I tested this by disconnecting it and saw marginally higher pressures but this is masking the underlying issue.

strutaeng

Ok, well it's looking like the oil pump needs to be removed and torn down for inspection to me. If the clearances aren't within specifications of the pump, no matter what you do elsewhere on the engine, pressure probably won't build up.

1redta

what oil are you using?

snives

It has Lucas 5w20 break in oil in it. I chose that weight because it closely matches what GM calls for in this vehicle, 0W20.

1redta

I’d try a heavier oil

snives

Update: I dropped the oil pan to check the oil pickup tube. There's no o-rings on the Gen V like there is on the Gen IV engines that could get pinched. However, if a pinched o-ring could cause aeration of the oil as it is drawn into the pump, like it does on the Gen IV LS then is it not also possible that a tiny air gap in the pickup on the Gen V could do the same thing? That was my theory, so I made a bit of a gasket myself with RTV around the pickup tube. Slapped it back on (actually meticulously reinserted and snugged down) and... didn't change a thing, damn. But, I've factored that out now. Not saying that's not the problem for some people, but it wasn't the problem for me. So, I've ordered a new pump. Will report back after that arrives.