NOT GMT400 RELATED. '09 5.3L oil pressure issue

[Schurkey]

Posting here 'cause I'm not a member of an LS-specific forum.

Friend has an '09 Silverado with low oil pressure at the rear of the engine--sensor and dash gauge shows ~20 psi when warm at idle, in neutral. Sets an oil pressure code. My friend replaced the sensor and the screen under the sensor. No change.

We tested oil pressure with a mechanical gauge at the lower left front oil port; my gauge shows 50 psi when the dash gauge shows 20.

Is there a common reason why the LS engine would lose half of it's oil pressure from front to rear?

 

[MIHELA]

Those LC9 motors have issues with cam bearings, oil pumps, lifters, pistons and rings, AFM lifters, cam wear and oil switch screens. They were constantly having oil consumption issues and cam failures when I worked at Chevy.

 

[stutaeng]

The guage says "20" and it's setting the low oil pressure light?

I don't have any experience on the Gen IV, but this thread has a link to a very informative article about them: https://www.gm-trucks.com/forums/topic/248591-2010-lc9-low-oil-pressure-fixed-by-oil-filter/

 

[MIHELA]

AFM requires a minimum of about 25 PSI to function.

 

[Supercharged111]

They also like to send shavings through the motor and futz up the oil pressure sending units and cause the pressure relief valve to stick.

 

[Schurkey]

Unlikely to be the sender or the screen, as both have just been replaced; and the new sensor/screen reads exactly the same as the original sensor/screen.

Can't be the oil pump/pressure relief, as I've got plenty of pressure at the front of the engine.

The issue is loss of pressure between the front and the back; which--I guess--means wiped bearings or restricted passages; or perhaps a restricted oil filter. I don't know where the oil filter is in that circuit--before or behind the front oil-pressure tap.

If there's a common cause for pressure loss from front to rear, I'd love to hear about it. Especially if there's an "easy fix".

 

[MrPink]

More than likely the cam bearings are wiped out. The LC9 is known for that, it will run perfectly fine aside from the oil pressure. The VLOM(valve lifter oil manifold) could be the culprit too but unlikely.

 

[MIHELA]

GM redesigned the cam bearings a long time ago and went with a teflon coated bearing. That should be a long term fix if that's the only issue.

 

[letitsnow]

Somebody has to say it...

I thought that these ls motors were a huge advance in quality and longevity? Just drop a 200,000 mile ls motor in and you are golden!!!

 

[someotherguy]

Somebody has to say it...

I thought that these ls motors were a huge advance in quality and longevity? Just drop a 200,000 mile ls motor in and you are golden!!!

*without AFM

Richard