No oil pressure at start up, 2001 Tahoe

[OR VietVet]

Overlooking the condescending tone in your post, my general answer is "because that is how they designed it". Additionally, I've periodically had my oil analyzed by Blackstone and historically all wear indicators were in line and of no cause for concern. Bottom line is, everything has been working well so I've been doing what the owner's manual calls for. If this most recent sample shows an increase in bearing wear, I'll happily change to a different oil if it'll counter the degradation inside my motor.

Stick with whatever works for you.

 

[clandr1]

Just changed the oil with Mobil 1 5w-30 high mileage and an AC delco filter. No change. I grabbed a sample and will send it off to Blackstone Labs for analysis before I do anything else.

I just received my oil analysis via email. It seems like good news. Here is their commentary:

Low oil pressure does usually mean bearing wear. Lead is the main indicator of how the bearings are doing, and lead looks alright compared to what we were seeing back in 2019. The other wear metals look fine too, given the interval, so there's no clear sign of what caused the oil pressure to drop. The viscosity is in the appropriate range for 5W/30 and no contamination such as fuel or coolant was found. Low insolubles means oil filtration is working properly. Try about 7,000 miles next time, but let us know if the low oil pressure continues.

I'm wondering if my oil pressure sensor is just going bad and/or getting gummed up (it is original). It seems I have three options in front of me:
1. keep driving it as is, and monitor the oil pressure for any further drop.
2. next time I come up on an oil change interval, run some seafoam in my crank case, hoping it will dislodge whatever sludge might be blocking my oil pressure sensor.
3. change the oil pressure sensor and see if it makes a difference.

Thoughts or suggestions from anyone?

 

[Tonyrodz]

I just received my oil analysis via email. It seems like good news. Here is their commentary:

Low oil pressure does usually mean bearing wear. Lead is the main indicator of how the bearings are doing, and lead looks alright compared to what we were seeing back in 2019. The other wear metals look fine too, given the interval, so there's no clear sign of what caused the oil pressure to drop. The viscosity is in the appropriate range for 5W/30 and no contamination such as fuel or coolant was found. Low insolubles means oil filtration is working properly. Try about 7,000 miles next time, but let us know if the low oil pressure continues.

I'm wondering if my oil pressure sensor is just going bad and/or getting gummed up (it is original). It seems I have three options in front of me:
1. keep driving it as is, and monitor the oil pressure for any further drop.
2. next time I come up on an oil change interval, run some seafoam in my crank case, hoping it will dislodge whatever sludge might be blocking my oil pressure sensor.
3. change the oil pressure sensor and see if it makes a difference.

Thoughts or suggestions from anyone?

In the long run it'll be cheaper to swap out to a new oil pressure sensor. That'll rule out any engine--oil pressure--issues early enough to take preventive action if needed. Just my opinion.

 

[Sam Harris]

I just received my oil analysis via email. It seems like good news. Here is their commentary:

Low oil pressure does usually mean bearing wear. Lead is the main indicator of how the bearings are doing, and lead looks alright compared to what we were seeing back in 2019. The other wear metals look fine too, given the interval, so there's no clear sign of what caused the oil pressure to drop. The viscosity is in the appropriate range for 5W/30 and no contamination such as fuel or coolant was found. Low insolubles means oil filtration is working properly. Try about 7,000 miles next time, but let us know if the low oil pressure continues.

I'm wondering if my oil pressure sensor is just going bad and/or getting gummed up (it is original). It seems I have three options in front of me:
1. keep driving it as is, and monitor the oil pressure for any further drop.
2. next time I come up on an oil change interval, run some seafoam in my crank case, hoping it will dislodge whatever sludge might be blocking my oil pressure sensor.
3. change the oil pressure sensor and see if it makes a difference.

Thoughts or suggestions from anyone?

I vote options 2 & 3. (2, then 3..)

Be sure to replace the sensor with a genuine Delco part too. I broke the first replacement, so had to use the crap brand at Oreillys and it not only gave up 3 months later, it actually sprung a leak, causing a real low oil pressure issue..!

 

[clandr1]

In the long run it'll be cheaper to swap out to a new oil pressure sensor. That'll rule out any engine--oil pressure--issues early enough to take preventive action if needed. Just my opinion.

I vote options 2 & 3. (2, then 3..)

Be sure to replace the sensor with a genuine Delco part too. I broke the first replacement, so had to use the crap brand at Oreillys and it not only gave up 3 months later, it actually sprung a leak, causing a real low oil pressure issue..!

Thanks fellas. After some research last night, I ordered an AC Delco oil pressure sensor (GM 12677836), a Lisle 13250 Oil Pressure Switch Socket, and a Lisle 39400 Angled Disconnect Tool Set. I understand it's easier to do the job without removing the intake if you can disconnect the fuel line, remove the PCV hoses, and have the right u joint and extension for the socket. I'll try to tackle it a week from tomorrow and report back.

 

[clandr1]

Well, this happened today. I guess we can firmly call this a sensor failure.

 

[Tonyrodz]

Well, this happened today. I guess we can firmly call this a sensor failure.



View attachment 279342 View attachment 279343

I'd say so.

 

[Fless]

Well, this happened today. I guess we can firmly call this a sensor failure.



View attachment 279342

I just reinstalled a cluster that I had redone (new steppers) for my neighbor, and the exact same thing happened. We can tell it has oil pressure by the lack of noise, so it has to be the sensor or the circuit.

 

[Sam Harris]

Well, this happened today. I guess we can firmly call this a sensor failure.



View attachment 279342

I went through 4, before it finally decided to keep working. [emoji35][emoji107]

 

[clandr1]

I just reinstalled a cluster that I had redone (new steppers) for my neighbor, and the exact same thing happened. We can tell it has oil pressure by the lack of noise, so it has to be the sensor or the circuit.

Strange, my cluster was just rebuilt in December by a guy who has a TON of experience and positive feedback - maybe just a coincidence? My gauges were working fine before the rebuild, and were working fine after until this recent drop in indicated oil pressure.

I went through 4, before it finally decided to keep working. [emoji35][emoji107]

Oh jeez, were all 4 AC Delco sensors? Hopefully that's not what's ahead of me...