Oil pressure/rebuild advice

[clandr1]

Well. Got a gauge. That thing is a freaking pain to get threaded into the sensor slot. But I put it on there, and ran the engine for probably like an hour and it never dropped below 30. Figured I ought to try to replicate the circumstances where the symptoms show up and whatnot, so I put the sensor back in and went for a drive. Drove about 30 miles, mix of city and highway roads. For the first 25 miles it held great, stayed up around 40, would drop down to 30ish sometimes. I had myself thinking I just had to turn the thing off and back on again to fix it. When I got closer to home it started dropping lower, between 10 and 20 at stops and holding around 20 while driving steadily around 35mph. Never did get low enough to ding at me but it was pretty close. So I pulled back in my driveway and immediately tried to get the gauge back on to see what it said. By the time I got it on (took probably 20 minutes, 4 scrapes and a burnt knuckle) the gauge was showing 30.



Something I thought of... do you think I could unscrew the hose from the gauge, screw the actual sensor onto the end of the hose, and plug it in? That way I could drive until I start getting warnings, hop out and unplug the sensor and screw the gauge back onto the hose and check it. I'd be much more comfortable doing something like that than drilling into things haha.

I think you'll need to leave the mechanical gauge connected while you drive around and see if it reads similar to what the sensor is reading based on prior experience.

 

[Mudsport96]

Well you could. Or see what thread pattern the block has, put in a "T" and run both off of the same pressure port. That way you are getting the reading at the same spot.

 

[willfalcon]

If the mechanical gauge reads good pressure, my next step would be to replace the sensor.

I think you'll need to leave the mechanical gauge connected while you drive around and see if it reads similar to what the sensor is reading based on prior experience.

Well, I've been driving around with the mechanical gauge attached the last few days. I'd go until it got hot and the dash gauge would normally be dropping super low, below 20, and giving me warnings sometimes when I stop. With the mechanical gauge attached, I'd stop, get out and check, and it would never be below 30.

So I'll order a new sensor. Is another ACDelco my best bet or are there any other recommendations?



Another thought. I was talking to a mechanic friend and half-jokingly asked if he wanted to help me figure out my oil pressure problems. And he said something along the lines of "Oh you're not gonna make me track down your 5 volt reference are you?" And I thought it was a joke at the time but now I realize, I guess theoretically if the sensor wasn't getting an accurate 5 volts it would send back an incorrect reading, wouldn't it? Dug around the wiring diagrams in alldata and it gets the 5volt reference from the pcm, which also sends 5 volts to the map sensor. (Also to the fuel tank pressure sensor and A/C refrigerant pressure, but it looks like those two are separate somehow). Is this a thing? Could the PCM be sending the wrong reference voltage after it starts getting hot?

 

[iamdub]

Well, I've been driving around with the mechanical gauge attached the last few days. I'd go until it got hot and the dash gauge would normally be dropping super low, below 20, and giving me warnings sometimes when I stop. With the mechanical gauge attached, I'd stop, get out and check, and it would never be below 30.

So I'll order a new sensor. Is another ACDelco my best bet or are there any other recommendations

With any electronics on these things, AC Delco, Delphi or Bosch (all dependent upon what item/system) are highly recommended.

Another thought. I was talking to a mechanic friend and half-jokingly asked if he wanted to help me figure out my oil pressure problems. And he said something along the lines of "Oh you're not gonna make me track down your 5 volt reference are you?" And I thought it was a joke at the time but now I realize, I guess theoretically if the sensor wasn't getting an accurate 5 volts it would send back an incorrect reading, wouldn't it? Dug around the wiring diagrams in alldata and it gets the 5volt reference from the pcm, which also sends 5 volts to the map sensor. (Also to the fuel tank pressure sensor and A/C refrigerant pressure, but it looks like those two are separate somehow). Is this a thing? Could the PCM be sending the wrong reference voltage after it starts getting hot?

Sure, it's a possibility, but quite a long shot. Even then, I wouldn't say the PCM would be sending a faulty signal- I'd look more at the wiring in between, particularly the plug ends. The sensor is MUCH more a likely culprit.

 

[clandr1]

An OEM AC Delco replacement is your best bet. I think it’s unlikely that your PCM is bad, but once you replace the sensor you’ll know what to do next if the problem persists.

 

[willfalcon]

Final update on this saga.

I followed a friend's advice of putting some seafoam in the crankcase.
After that had been in for about 150 miles, I followed yall's general advice and my conscious and changed to a better oil and filter.
And then replaced the oil pressure sensor.

Been a little over 700 miles and no issues. Never drops below ~35psi.

If I wasn't so desperate I would have done those things a little more spaced apart from each other to really see how each one affected it, but I mean, it was probably just the pressure sensor right?

In case anyone wants to know, I used Valvoline high-mileage synthetic blend 10w-30 and a K&N HP filter.

 

[clandr1]

Final update on this saga.

I followed a friend's advice of putting some seafoam in the crankcase.
After that had been in for about 150 miles, I followed yall's general advice and my conscious and changed to a better oil and filter.
And then replaced the oil pressure sensor.

Been a little over 700 miles and no issues. Never drops below ~35psi.

If I wasn't so desperate I would have done those things a little more spaced apart from each other to really see how each one affected it, but I mean, it was probably just the pressure sensor right?

In case anyone wants to know, I used Valvoline high-mileage synthetic blend 10w-30 and a K&N HP filter.

Thanks for the update and closing the loop with us. Glad you got it worked out.

Were you using a high mileage blend previously? If not, I highly recommend using it moving forward. My own personal experience: I switched to Mobil 1 5W-30 High Mileage synthetic when my truck hit about 75,000 miles (I've owned it since new) and it now has ~225,000 on it. My Blackstone Labs oil analysis have always come back showing everything looks great, and the only time I've ever had an issue with oil pressure was when my pickup tube o-ring failed about 3 years ago.

The Mobil 1 high mileage oil has served me very, very well. As I understand it, the high mileage variants have detergents in them that keep the motor clean and prevent sludge buildup.

 

[Mudsport96]

While i agree a quality filter is the best option, as long as you stick to a good oil change regimen even decent oil works. My Silverado has 400k on the clock and the father in law had it its whole life before i got it. He used Castrol from new till the warranty was up then ran oriellys house brand since 120k to 394k when he gave it to me for my daughter.

 

[willfalcon]

Thanks for the update and closing the loop with us. Glad you got it worked out.

Were you using a high mileage blend previously? If not, I highly recommend using it moving forward. My own personal experience: I switched to Mobil 1 5W-30 High Mileage synthetic when my truck hit about 75,000 miles (I've owned it since new) and it now has ~225,000 on it. My Blackstone Labs oil analysis have always come back showing everything looks great, and the only time I've ever had an issue with oil pressure was when my pickup tube o-ring failed about 3 years ago.

The Mobil 1 high mileage oil has served me very, very well. As I understand it, the high mileage variants have detergents in them that keep the motor clean and prevent sludge buildup.

I was using high mileage, but it was just conventional supertech. I watched a testing video on youtube, guy ran a bunch of tests on a few different brands including supertech, plus valvoline, castrol, royal purple, etc. Super tech wasn't as good in those tests as the big brands but it wasn't that drastically worse, so I went with it for a while... ¯\_(ツ)_/¯ I'll stick with what works from now on I guess.

And yeah that's what I understood about the high mileage oil as well. Possibly a part of it that reconditions rubber seals as well

 

[clandr1]

I was using high mileage, but it was just conventional supertech. I watched a testing video on youtube, guy ran a bunch of tests on a few different brands including supertech, plus valvoline, castrol, royal purple, etc. Super tech wasn't as good in those tests as the big brands but it wasn't that drastically worse, so I went with it for a while... ¯\_(ツ)_/¯ I'll stick with what works from now on I guess.

And yeah that's what I understood about the high mileage oil as well. Possibly a part of it that reconditions rubber seals as well

Ah yes, Project Farm! I love that channel and saw the same video.