Scotty, my 2003 Silverado 4.8L automatic with 184,000 miles shows as low as 15 psi oil pressure, with engine idling at normal operating temp, in gear, with a/c on, when stopped at a traffic light. Over the past year, the oil pan gasket, oil pickup o-ring, valve cover gaskets, rear main seal, intake manifold gasket, #2 knock sensor and connecting wires, and oil pressure sending unit were replaced. Prior to that work, the gauge showed 35 psi at idle. A check with an external gauge confirms the in-dash instrument is accurate. It does not smoke, nor leak, and there is no oil in the coolant. What do you think? How low can oil pressure get before it is cause for concern? Is it time for a compression check? thank you
15PSI is low, but the LR4 engine didn't have AFM or VVT, so low pressure shouldn't cause too much trouble. If the oil light doesn't come on then you're probably OK, but it's getting close. I don't think a compression check will help you much with that problem. I think I would just baby it, keep going and try to get as many miles out of it as I could.
I take it back. 15 PSI is within spec. 35 PSI at idle is much too high.
These are hot oil pressure specs for the LR4 engine:
6 psig at 1,000 engine RPM
18 psig at 2,000 engine RPM
24 psig at 4,000 engine RPM
https://www.engine-specs.net/gm/lr4.html
I have to disagree. Every spec I lookup on that motor says 30-35 at idle. Up to 60 at higher rpms. 15 psi is doing damage.
That link shows 41 kpa which converts to 5.9 psi. Can’t be correct, sorry.
keep in mind these are minimums. 15 PSI is still a decent amount of pressure. It means the oil is moving through all parts. I don't see any reason why it would be doing damage.
Well Ive built and rebuilt enough engines to know 6 psi is barely getting oil into the bearing race. And I have known GM to publish wrong information before. Wouldn’t be the first time. I also know from experience 30-35 is normal at idle for these. Anything less than 20 is causing bearing, lifter, rocker and cam lobe wear. Understand your position and hate to disagree but with all respect I know those specs are wrong.
fair enough, but I have two sources: the website, and GM database. Can you link some other publication. A service manual or something which shows different?
On a side note when I have seen low oil pressure below 20 it’s either a bad pump, major oil leak, restriction in flow, or the bearings are so worn they system can’t produce pressure.
Do you realize that indicated pressure changes as the engine wears? Of course when the bearings are new they present more of a resitriction, so oil pressure could indicate 35 PSI or more. As they wear, tolerances increase, and the pressure required to pump oil through them goes down.
Many blog entries from other owners in same type of forums stating theirs run 30-35 at idle. The entry owner of this blog saying theirs was 30-35 normally. Experience. I found the information you posted. And Im saying its a misprint. I’ll call dealer in morning find out. No way is 6psi at 1000 rpms correct. Even 15 is way to low. Learned a long time ago never trust publications when your experience tells you otherwise.
Blogs aren't a credible source.
I made the mistake of letting a shop do my wife’s 2001 Safari 4.3 V6 intake manifold gasket. It was a van, cramped, hard to get to, so was worth the money pay to get it done. However the tech that ended up doing it was young, lazy, most of the old gasket material when he cleaned it off he let fall into the engine. Day I picked it up I was using it to tow a trailer. On the way I noticed everytime we stopped at a light oil pressure dropped to 20 PSI. On the interstate later it dropped to 0 and spun two bearings before I could kill it and pull over. Gasket material had clogged the oil pickup scoop and screen. Wouldn’t be surprised with all you have had done if you didn’t have a similar issue. Your gonna have pull the pan either way to figure it out. Trash in the pickup or new oil pump.
At 15 psi your doing damage. Stop driving it til it’s fixed.
If it is trash in the pickup, I bet you good money it’s from the intake manifold job. I would have whoever did that work pay to fix it. Business that did mine paid to replace my engine. Took a year, but finally they caved.
Yea, and I spoke with GM back during that incident. Those figures are wrong.
Spoke with the Lead Service tech at Priority Chevrolet in Newport News Va today. Those specs published by GM are not real world applicable specs. They are minimum acceptable pressure in a lab/dyno environment with absolutely no load on the engine. Normal oil pressure real world application for the 2003 4.8L is 30-35 PSI ar idle and 40-60 at speed. Specs allow for slight deviation for wear. 20psi being the lowest acceptable pressure at 1,000 rpms. Any lower and your causing damage and excessive wear. His exact words to me when I asked if 15 psi was ok.
"They are minimum acceptable pressure ... with absolutely no load on the engine."
It literally says "minimum" in the screenshots, and I stated that in my post. And yes, when you're idling there is almost no load on the engine.
also, a chassis dynamometer is meant to load the engine. {black}:idontknow:
That's why people use it to measure torque/hp
https://en.wikipedia.org/wiki/Chassis_dynamometer
" informally referred to as a rolling road,"
So you’re saying the lead service tech at a Chevrolet dealership who had been doing this for years is wrong and that 6psi is an acceptable oil pressure in a V8 engine. I know any engine running that is destined for death. No load means no torque converter, nothing on the crankshaft pulley. Before any load is applied. Anyway I’m just trying save the guy an engine. You seemed to be more interested in proving yourself right. Let’s just ask Scotty see what he says.
I've met too many people who claimed various titles, but turned out to be complete dingbats. So no, I don't take them at face value any more. Lead tech just means he's got the most seniority at his shop, which doesn't mean much. I provided at least 5 different sources now for the same numbers. The likelihood that that they're all wrong is extremely slim. The numbers actually look about right when I look at my pressure gauge. 6PSI would be red tick marks.
In park gear, the torque converter presents a negligible load. Maybe a ft-lb or two.
I stand by my original statement. The oil pressure is low, but not yet in the "red". The engine is probably not in the greatest shape, which is unsurprising @184k miles. He already dropped the pan and did the bottom end work. Short of rebuilding, there may not be much he can do. That's why I said baby it and ride it out. A 4.8L is small V8, and if it was driven hard, it could easily be worn out.
I would suspect that the oil pickup o-ring was either crimped or not installed at all. Who did the work, you or someone else; dealership? I would drop the oil pan and check the pick up tube intake screen and the o-ring. Most people can fart more than 6 psi.
