Oil pressure drop?

[kchamber]

After about 1.5 hours on freeway. Came to stop in town and oil pressure dropped below 20. Is that normal ?
Just got a new sending unit and oil pump.

 

[wjburken]

View attachment 268742 After about 1.5 hours on freeway. Came to stop in town and oil pressure dropped below 20. Is that normal ?
Just got a new sending unit and oil pump. View attachment 268743 View attachment 268744

Why did you get a new pump and sending unit? What pump did you go with? Does the pressure increase when you are up to speed?

Can’t say that it’s too alarming, yet, but would definitely pay close attention since you just had work done on the oil system.

 

[Geotrash]

+1. That's on the low end of normal for a stock oil pump after highway driving on a higher mileage engine. Not normal if there's a new oil pump and pick-up tube o-ring in there, assuming they replaced the oil sending unit screen when they replaced the sender. More details on the work if you have them, please. It would also help to know which make and model oil pump they put in.

 

[OR VietVet]

Did you do the work yourself? Did you replace the sending unit screen? Did you replace the pickup tube o-ring? Why was the sending unit and pump replaced? Did a shop do the work? The invoice should have a detail of what was done and why and what parts were used.

At this point you should also attach a gauge and get a reading at cold start, warm up and after being driven on the highway.

 

[ls1frc]

It idle my 5.3 was about that. My 6.2 with all new stuff is also about that. If it kicks right up with rpms, I wouldn't worry too much. My 5.3 with a non vvt cam was higher than stock, so might just be the VVT lowering it a bit at idle.

If you hear audible engine noise and the oil psi doesnt come up with rpms then you have a problem.

 

[wsteele]

My ‘07 5.3L, original engine, idles about 28-30 PSI after a long freeway run. 5W-30 synthetic. My oil pressures have always been strong (or my sender/gauge weak).

Having said that, if it had that reading after a couple hours at freeway speed, I wouldn’t be concerned.

What did it register before you got off the freeway?

 

[kchamber]

Why did you get a new pump and sending unit? What pump did you go with? Does the pressure increase when you are up to speed?

Can’t say that it’s too alarming, yet, but would definitely pay close attention since you just had work done on the oil system.

My sending unit failed - then the mechanic stated that the pump was ultimately scarred and failed.

 

[Geotrash]

My sending unit failed - then the mechanic stated that the pump was ultimately scarred and failed.

Strange conclusion for him to make, since there is no way to tell if the pump is damaged without pulling it, which is a fairly major job on these engines. And... the oil pump is seldom the culprit of low oil pressure on these engines.

Also, there are a few different oil pump options. Your engine has VVT which requires a high volume pump. Hence why 2 of us have asked which pump the mechanic put in. If it's the wrong one, you would have a reasonable case to go back to him and ask that he put the correct one in.

As I said, your oil pressure is on the low end of normal in my opinion, but okay to run. Just keep an eye on it

 

[kchamber]

Strange conclusion for him to make, since there is no way to tell if the pump is damaged without pulling it, which is a fairly major job on these engines. And... the oil pump is seldom the culprit of low oil pressure on these engines.

Also, there are a few different oil pump options. Your engine has VVT which requires a high volume pump. Hence why 2 of us have asked which pump the mechanic put in. If it's the wrong one, you would have a reasonable case to go back to him and ask that he put the correct one in.

As I said, your oil pressure is on the low end of normal in my opinion, but okay to run. Just keep an eye on it

So to clarify. Replaced sending unit because it had failed. After replacing sending unit. Oil pressure still wasn’t normal. Thus they deemed it to be the unit. They said after pulling it It certainly had scarring.

 

[OR VietVet]

So, to clarify, the tech(s) decided that the oil pump needed replacing because the sender did not fix but did not put a mechanical gauge on the engine to verify oil pressure? Did they show and explain the "oil pump scarring"? I am assuming, maybe wrongfully so, that the scarring they talked about was caused by too many miles between oil changes, poor quality oil or contamination in the oil, like coolant or fuel, that would break down the lubricating properties of the oil? I just always backed up any diagnosis with the reasons for it and showing the problem(s).

 

[Geotrash]

So to clarify. Replaced sending unit because it had failed. After replacing sending unit. Oil pressure still wasn’t normal. Thus they deemed it to be the unit. They said after pulling it It certainly had scarring.

Thanks for clarifying. There are 2 pieces that are still missing for me to offer clear guidance:

1. Whether or not they replaced the filter screen that sits under the oil pressure sender. Lots of people make the mistake of replacing the sender not knowing there's a screen under it that's hard to get out and probably 90% of the time the cause of low oil pressure on these engines. My guess is that if the oil pressure didn't change significantly after the pump replacement, that the pump wasn't at fault.
2. Whether or not they replaced or accidentally damaged the o-ring on the oil pump pick-up tube when they replaced the pump.

Those 2 items alone are responsible for maybe 98% of low oil pressure issues on these engines. After that it's a mixture of leaking VLOM seals, worn cam bearings, a bad oil pressure relief valve at the rear of the oil pan, or a leaking dog bone in the rear of the block.

 

[OR VietVet]

Just for info sake, here is a pic of the sensor and the screen: https://www.rockauto.com/en/moreinfo.php?pk=9452316&cc=1441073&jsn=1902

 

[kchamber]

Thanks for clarifying. There are 2 pieces that are still missing for me to offer clear guidance:

1. Whether or not they replaced the filter screen that sits under the oil pressure sender. Lots of people make the mistake of replacing the sender not knowing there's a screen under it that's hard to get out and probably 90% of the time the cause of low oil pressure on these engines. My guess is that if the oil pressure didn't change significantly after the pump replacement, that the pump wasn't at fault.
2. Whether or not they replaced or accidentally damaged the o-ring on the oil pump pick-up tube when they replaced the pump.

Those 2 items alone are responsible for maybe 98% of low oil pressure issues on these engines. After that it's a mixture of leaking VLOM seals, worn cam bearings, a bad oil pressure relief valve at the rear of the oil pan, or a leaking dog bone in the rear of the block.

The pump peformance is certainly better. Before oil pump replacement it would bottom out at startup and the notification for low oil pressure shut off vehicle would come on. So it’s better than it was. I just don’t recall if the photo provide in the original post was in usual range. Another twist is that I live at 7000 feet. Might not matter. But an additional detail.

 

[OR VietVet]

As far as I know, the elevation will effect air density, vacuum readings but not mechanical oil pressure readings. Were you shown the "scarred" oil pump damage? Did they ever put a mechanical gauge on the rig before oil pump replacement? I understand you are satisfied with the results but I gotta ask. Was the sensor screen ever mentioned or replaced?

 

[kchamber]

As far as I know, the elevation will effect air density, vacuum readings but not mechanical oil pressure readings. Were you shown the "scarred" oil pump damage? Did they ever put a mechanical gauge on the rig before oil pump replacement? I understand you are satisfied with the results but I gotta ask. Was the sensor screen ever mentioned or replaced?

They did show it to me. Never was a sensor screen mentioned.

 

[wjburken]

The pump peformance is certainly better. Before oil pump replacement it would bottom out at startup and the notification for low oil pressure shut off vehicle would come on. So it’s better than it was. I just don’t recall if the photo provide in the original post was in usual range. Another twist is that I live at 7000 feet. Might not matter. But an additional detail.

I hate to say it, but I would not be surprised if the true cause of your oil pressure issues was a cracked/failed o-ring that happened to be replaced when they swapped the pump, but if it was scarred, I could be wet in the head on this as well.

As @PNW VietVet mentioned, along with the o-ring, the screen is a very common source of oil pressure issues and if the shop didn't mention it, I would definitely look into getting a new screen or, at a minimum, cleaning the one you have.

 

[OR VietVet]

I have noticed on RA that when you look up the sender for my 2005 5.3 it will show a sender and also a screen depending on the manufacturer. Not to worry though. The screen started with the engines with AFM.

 

[chilleblanco36]

I chose to post here rather than start a new post. I just noticed my oil pressure harboring around 20 psi at idle during normal operating temperature. I checked it this morning during cold start and it only went to like 35 psi. Never over 40 psi.

after reading I plan to change the sending unit and the screen/filter before going into replacing the oil pump. It does raise with RPM’s, but never over 40 psi. Only to like 35 or so. Thoughts?

 

[Foggy]

I chose to post here rather than start a new post. I just noticed my oil pressure harboring around 20 psi at idle during normal operating temperature. I checked it this morning during cold start and it only went to like 35 psi. Never over 40 psi.

after reading I plan to change the sending unit and the screen/filter before going into replacing the oil pump. It does raise with RPM’s, but never over 40 psi. Only to like 35 or so. Thoughts?

I think are ok with that oil pressure.. Just make sure you keep quality clean synthetic oil
in it 5w30 or 5w40. And use a high quality oil filter like wix

 

[OR VietVet]

@chilleblanco36, You may well have a partially clogged screen in that sensor line. I have read many a thread about low oil pressure fix with a new screen and sensor. And, please, whatever you do, do not use a cheap set of parts. I would look up the parts but like happens so many many times, someone posts a question or a problem and gives no vehicle info. I cannot stress this enough: "These rigs are not all the same"! Different years, models, engines....etc.