Chevy 5.7L; 1999; Oil pressure issue

Question

Chevy 5.7L; 1999; Oil pressure issue

DAVIDSTECKER (Mechanical)

(OP)

24 Jul 23 18:32

Recently my check gages light has been coming on, and when I looked the oil pressure was dropping to almost zero.
This only happens when I come to a stop and the engine is up to temp.
This also seems to happen only when I've been running the AC.
Putting the trans in to neutral and a quick tap of the throttle and the pressure goes back up to about 10-15 PSI.
I have also been keeping an eye on the voltage gage and it does seem to be a little lower when running the AC which makes some sense, although I have a 105 Amp alternator.
The engine does have 312,XXX miles on it, but it doesn't burn oil and no sounds that would indicate rod or crank bearing issues.
I ran across this YouTube video that exactly describes what I experiencing.
https://www.youtube.com/watch?v=SsrxBVerNAw
My question is, does this sound plausible or have you ran across this issue before, and if so was this the cause or was it something else.
Best regards, David

TugboatEng (Marine/Ocean) · Answer 1 · 2023-07-24 20:30:37

The front cam bearings wear out and cause low oil pressure on the older GM V8 engines.

DAVIDSTECKER (Mechanical) · Answer 2 · 2023-07-24 21:35:04

Hey Tugboat, Thank you once again for your input, always appreciated.
Yes, I was mostly concerned about the bearings and possibly the oil pump until the video.
Something that I was considering is a product I ran across some time ago, TriboTEX.
I've been looking around to see if there was any merit to their claims or if it was more snake oil.
Years ago I was sceptical of Prolong additives until I put some in my old manual transmission running 90wt.
Even below freezing, it shifted as if it was 90deg.
Amazing difference.
Do you or anyone else have any experience with TriboTEX?
Best regards, David

XR250 (Structural) · Answer 3 · 2023-08-02 16:33:02

I would try heavier engine oil. I think you are supposed to have 10 PSI per 1000 RPM.

DAVIDSTECKER (Mechanical) · Answer 4 · 2023-08-02 16:38:59

XR250, That was going to be my next step.
My 1993 5.7L runs 10-30W, so I was going to change to that since issue is sort of intermittent.
Thanks for your input, David

enginesrus (Mechanical) · Answer 5 · 2023-08-10 07:56:32

Does it use a variable displacement oil pump? One of the most nonsensical devices applied to any engines lube system.

gruntguru (Mechanical) · Answer 6 · 2023-08-11 02:25:43

Makes perfect sense. Saves fuel otherwise wasted pumping oil through a pressure relief valve.

je suis charlie

TugboatEng (Marine/Ocean) · Answer 7 · 2023-08-11 03:15:50

Especially when modern engines use the engine oil as hydraulic fluid to reliably control things that 1950's vacuum doesn't work so well for. To do this a large enough pump to provide more than 5 psi at idle is required but that same pump would become quite parasitic at any higher speeds.

Add to that, many engines don't make as much vacuum as they used to as pumping against a closed throttle plate is another parasitic loss.

BrianPetersen (Mechanical) · Answer 8 · 2023-08-11 04:05:18

Chevrolet small-block V8 engines use a fixed-displacement gear pump. On the LS engines (which is probably what this is), it's a gerotor pump at the front of the engine driven by the crankshaft. No blaming the variable-displacement mechanism in this one.

I suspect she's pretty tired.

TugboatEng (Marine/Ocean) · Answer 9 · 2023-08-11 05:42:37

OP is asking about the Vortec engine which is mostly the original small block with some really good heads and a decent multi port fuel injection system as well as a roller cam.

Enginesrus is referencing the late-2000's+ 4th and 5th Gen engines with cylinder deactivation. Those engines also have variable displacement oil pumps.

How his comments contributed to the conversation is beyond me.

enginesrus (Mechanical) · Answer 10 · 2023-08-11 18:16:19

RE: Chevy 5.7L; 1999; Oil pressure issue

enginesrus (Mechanical) 11 Aug 23 18:16

It was a question, so yes a contribution.

DAVIDSTECKER (Mechanical) · Answer 11 · 2023-08-14 13:20:26

Tugboateng, At least I'm getting some responses.
Having a Roller Cam is something I did not know so I'm happy with the deviation. LOL
Sorry I didn't chime in earlier; I was on vacation.
Thanks to all of you for your comments.
Best regards, David

Come Join Us!

Posting Guidelines

Chevy 5.7L; 1999; Oil pressure issue