Confused about oil pressure measurements

So over the past couple days I added seafoam to the oil. Started with 1/2 can and let idle for 30-45 mins several times over two days. I added the other 1/2 can and allowed truck to idle 30-45 mins a few times. Lastly I let truck get up to temp and and drained oil. I don't see any indication of chunks of crud or glitter in oil, but my eye is untrained. I will reinspect oil tomorrow and cut open filter. .

I filled with 5w30 and a put on Toyota filter. I drove around for an hour and the oil pressure behaved much better than previous drives. I will likely add more seafoam and do some driving and change oil at least 2 more times.

I can't really get up past 50 for long because on the next problem I will tackle, shaking/vibration.

Appreciate all the guidance and input!!!!

 

Curious to hear your results. Im having a similar issue with my T100. 25psi at idle and 75psi at 3000 rpm. Light comes on for a second on start up then goes off. Usually get a glimpse of it again when putting it into drive and when downshifting climbing hills. I did just run seafoam through it and drove about 80 miles and changed the oil. I don't think its made a bit of difference. Going to try taking it for a drive with the pressure guage installed soon and see if I notice anything odd. 355k so I can't really complain if it dies...

 

I know as per a chevy engine you want to see 10lbs oil pressure per 1k rpm so for example an engine turning 2500rpm you should see 25 psi oil pressure

Also low oil pressure can be caused by a worn oil pump pressure relief spring

 

The mechanical gauge gave me much more insight into my issue so I would say good idea. If you haven't changing the oil pressure sending unit to remove that variable from the equation might help isolate. 355k!!! Sweeet!

 

Think I'm dropping the pan tonight. Driving to work this morning I noticed it's pretty consistent when it has a higher demand for oil the light comes on for a second. Don't quite get why the light doesn't come on with the sensor plugged in, just not installed. I did replace the sensor and it reads the same as the old one.

 

https://youtu.be/U1vTY6CfTrY

Oil pressure a bit more consistent after some seafoam and oil change. It still I'm cautiously optimistic.

 

The service manual states

At normal operating temperature
Idle - 4.3 psi or more
3,000 RPM - 36 -75 psi

The biggest issue is WHEN the light comes on.
I don’t know the exact psi it comes on at, never seen any specifications for that?


I’d do what @Bishop84 suggested if the light continues to come on.

 

I agree dropping pan is the best course of action. Bored a scope and got a view into the crankcase where I can see lots of crud.

I did a lot of driving yesterday after oil change and the gauge didn't get below 5 PSI where as before it was falling into the solid black area after a period of driving.

 

lite usually come on late....................not usually early

low oil pressure underlight load not as damning as high rpm/load

still NOT good

the lower main/rod bearing suffer.........usually starve for oil

at idle the rings will survive occasional low pressure/supply

upper engine valves are least effected

 

Took mine for a drive tonight and saw no indication of the pressure doing anything abnormal. 10psi is as low as it goes. Starting to lean towards a loose ground somewhere. Realized the light won't come on with sensor not installed because it's an open circuit. I'm sure if I ground it it would. Closed circuit is low oil pressure.

 

I know is an old thread but the oil pressure light comes on at 2psi. Was told that is normal for the 3.4l to peg 80psi on cold start, run around 20-40 at a good rpm warm and as low as 4psi at warm idle.. friggn crazy.. mine runs kind of like this, 80 and 20’s warm idle but i always run a little lucas thickness oil snot in my oil then put in seafoam for the last few hundred miles before i change it and always run a half a quart of clean through like a super mini flush. Its got almost 200k and 200psi compression across the board on a cold crank.. only issues its got is a damn evap code and it does this thing where it feels like its pulsing when acceleration like youre tapping your foot on the throttle every second.. but its done that for years. Cant figure out why but it sure is annoying.. but idles @≈700.. sometimes 5w sometimes 0w.. oh and i got the damn issue where gas pump shuts off trying to fill it and ive blown out every vent, checked every valve and charcoal box, opened the tank and removed the flapper inside the thing, but still.. no clue.. yep.. my 2¢..