Mine has always read 40-45 at idle, 55-60 when driving. I've heard above 15-20 at idle is fine.
Oil pressure dropping
- Thread starter Musicars
- Start date
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Idle looks close to normal- mines about 700 but yours looks to be 500 according to your tach? I forgot that after a new pump my pressure is about 60 at idle. Ask them if they checked pressure with a manual gauge so you can rule out a problem with your gauge. Is it possible that someone has replaced stepper motors or your gauge face and didn’t get the pointers back on right so your gauges are off? If you have access to a cluster from a 2000-2006 Tahiti/suburban/Tahoe it pickup you can swap them for a minute to compare the readings on the gauges. Otherwise if it’s not knocking and there’s no warnings you should be ok.
Edit: I just noticed your volt gauge appears to be off so my theory of someone messing with the pointers seems more and more possible.
Edit: I just noticed your volt gauge appears to be off so my theory of someone messing with the pointers seems more and more possible.
Your gauge is reading exactly the same as mine does right now after I replaced my o-ring, both at idle and at 1000 RPM. It's a little higher when cold. It used to sit at around 40 psi. I have not done the pump yet.
Mine was lower before the o-ring and triggering the "Low Oil Pressure" warning. Is this current reading the same reading you were getting before the repairs or was it lower before the repairs?
This is very close to before repairs but when driving it now goes up around 35 if the RPMs are up. Prior to repairs it was not getting that high.
The shop is telling me that the rear main seal can be problematic for oil pressure but I had that changed last month with my flex plate replacement so it shouldn't be a problem. I'm waiting for the transmission shop to call back with the part numbers they put on for the rear main seal...hopefully they did both pieces and not just the gasket!
My other lead(s) have to do with Rocket Man's suggestions about stepper motors above...I'm trying to find out if my bluetooth ODBII reader will give me an oil pressure reading on my app...if not, I'll have to get an external gauge to try.
The shop is telling me that the rear main seal can be problematic for oil pressure but I had that changed last month with my flex plate replacement so it shouldn't be a problem. I'm waiting for the transmission shop to call back with the part numbers they put on for the rear main seal...hopefully they did both pieces and not just the gasket!
My other lead(s) have to do with Rocket Man's suggestions about stepper motors above...I'm trying to find out if my bluetooth ODBII reader will give me an oil pressure reading on my app...if not, I'll have to get an external gauge to try.
I looked with my Tech II and it doesn't show actual oil pressure so I'm thinking it isn't available through the system although I don't know why it wouldn't be. It shows whether the oil level switch is working and whether the low oil pressure has been triggered so I dunno. As far as aftermarket oil gauge, I'd suggest just getting the dash one calibrated if it's off. You could rent or buy a mechanical gauge and see what the pressure is at idle and 1000 rpm and set your cluster needle so it's correct. There's a way for an instrument cluster repair place to calibrate the gauges so that's another possibility if it's off.
I can't find oil pressure as an option in my app (or an additional app I tried) just like you said. I picked up a mechanical oil pressure gauge but ran out of time this weekend before I could put it on the truck to test my actual pressure. Maybe tomorrow it will happen.
Just reporting back with were I am at since the start of this thread. Finally got the new oil pump in. Started it up and the pressure is right were it was when I started this pain in the rear project.
Drove around and made notes. Highway from 55 mph to 70 mph the oil pressure sits steady at 30 psi. Driving around town it runs 20 psi to 25 psi. It idles with 10 psi. Last night I shut it off and restarted and the oil pressure was just below 10 psi. I'll have to see what happens today.
Very frustrated and not sure what to do from here out. Still find it weird the way this dropped pressure over just a few days. In the past worn bearings seem to gradually get to this point. There were some tiny flakes of metal in the pan but I would have expected more unless they were trapped in the filter. Even more frustarting is that the last couple of times I have gone to mechanics I have found them to not be reliable so I'm not even sure who to take it to. Sounds like keeping this truck is going to be expensive.
Drove around and made notes. Highway from 55 mph to 70 mph the oil pressure sits steady at 30 psi. Driving around town it runs 20 psi to 25 psi. It idles with 10 psi. Last night I shut it off and restarted and the oil pressure was just below 10 psi. I'll have to see what happens today.
Very frustrated and not sure what to do from here out. Still find it weird the way this dropped pressure over just a few days. In the past worn bearings seem to gradually get to this point. There were some tiny flakes of metal in the pan but I would have expected more unless they were trapped in the filter. Even more frustarting is that the last couple of times I have gone to mechanics I have found them to not be reliable so I'm not even sure who to take it to. Sounds like keeping this truck is going to be expensive.
swathdiver
Full Access Member
Tiny flakes is a sign that something is up and not right Joel. Have you sent the oil out to be analyzed? They may be able to decipher what kind of material is in the oil and whence it came from. Seems to me though, after all the work you've done, that it's time to put new bearings in it; time to freshen up the bottom end.
I have exactly the same result...same pressure after as before but not dropping to 0 ever. On the mechanical gauge I picked up it matches the dash. I’ll be driving this truck until it fails because I’ve paid for it twice now if you add up the repairs!
I figured that even though the particles are tiny that they should not be there. Since they don't appear to be magnetic I can only assume it is bearing material. I wish there was a way to find out which bearings. Probably crank bearings but I have heard of cam bearings going out too.
I have not sent the oil out. I'm not even sure who to send out to but will look into that. I kept what I could of the particles from when the I dropped the pan. I would probably have to use the current oil because I have been so busy I am not sure I didn't co-mingle the old oil from the truck with other oil. I have my truck, the wife's car, and my daughters car and have done a few oil changes lately. I suppose the current stuff is as good a test subject as any.
I'm going to try to see if I can find the serial number on this motor. I see something up by the oil filter on a pad but can't read it. If this is the original engine I would like to keep it and repair it. If not I may look at a different motor.
Yes, these motors are not cheap to repair or replace. I hear aboout all these motors going to nearly 300,000 miles and some way more so I expected more. But who knows how it was treated before.
My big fear is it breaking down on a long haul. Planned on taking it up north to put the dock in this weekend. A little leery of that now.
Curious as to where you hooked up the mechanical gauge. I assumed it had to be connected to the same place as the original sensor.
clandr1
Full Access Member
Blackstone Labs is the gold standard in oil analysis. I've sent numerous samples to them.
https://www.blackstone-labs.com/
Thanks, I had just found then on the internet and was about ask if anyone used them. Their FAQ section cracked me up but also had me concerned that their turnaround time might be a little slow. I'll give them a shot.
Took the truck on 125 mile trip north this weekend. Started at 30 psi of oil pressre on the highway. At about 100 mile the pressure was at about 27 psi on the highway. By the time I got up there it was still at about 27 and then idled with about 8 or 9 psi but the warning never was triggered. Then the next day drove 60 mile south to a funeral and sixty miles back up north with oil pressure starting at 30 then maybe ending at 27 - 28 psi. Drove the 125 mile back with the same pressure. It was a hot weekend with temps in the 80s and 90s in town and 70's and 80s up north.
There is one change. We noticed a weird scratchy rattle when I rev the engine. It does not follow the rpm exactly it kind lags the way a cracked flex plate sound lags but it does not sound like a flex plate. Sounds near the front of the engine but not sure if it is on top. Have to wait until I can get the wife to run the throttle while I use a stethoscope on it. It make the sound at idle but gets louder as it revs.
I am still surprised the oil pressure dropped so quickly originally but has not continued dropping significantly.
There is one change. We noticed a weird scratchy rattle when I rev the engine. It does not follow the rpm exactly it kind lags the way a cracked flex plate sound lags but it does not sound like a flex plate. Sounds near the front of the engine but not sure if it is on top. Have to wait until I can get the wife to run the throttle while I use a stethoscope on it. It make the sound at idle but gets louder as it revs.
I am still surprised the oil pressure dropped so quickly originally but has not continued dropping significantly.
clandr1
Full Access Member
Have you tried running seafoam in the oil? Only thing I can think of is there's a blockage of some sort in your pickup tube and it's causing the pressure to be low as a result. You've already replaced the pick up tube o-ring and the oil pump, right?
Have not tried Seafoam, but I did squirt brake cleaner down the pickup when I had it out. I never actually checked to make sure the tube was completely open but the brake cleaner ran through easily in both directions and the screen was clean when I took it out.
Also, I found the source of the rattling noise. I used a long wooden dowel as a "stethoscope" and tracked it down to the A/C tensioner. I saw another thread on this site discussing this issue. Now I just have to figure out if it was just the tensioner, the clutch, or the compressor. In my case it was louder with the A/C off and got better with it on. Later in the day it threw the belt so something stopped turning. Never squealed, just rattled.
The fun never stops!
clandr1
Full Access Member
The good news is the A/C belt tensioner is cheap and relatively easy to replace. I just installed one about three months ago. Sorry you're having trouble tracking down the oil pressure issues, I know it can be frustrating.
