Strange oil pressure issue

Jeff Dufour · May 13, 2020

Hi and thanks for reading. I hope I'm posting this in the right discussion.

I recently bought a used GMC Yukon xl 2004 and I have a strange oil pressure issue. Here's the story of my 7 oil change

1: bought truck, oil change was recent, drove about 5000km (3000 miles) pressure was normal and suddenly the oil pressure dropped, to zero. Checked oil level: normal.. Restarted truck: pressure ok.. I changed the oil.

2 fresh oil: Castrol and FRAM filter, drove about 4000km (2500 miles) again oil pressure dropped to 0...stop, wait restart, oil pressure isn't perfect, but enough to drive.. Did oil change..

3 fresh oil, Castrol and FRAM filter.. Pressure back to normal. Left for a long trip from west coast to the east coast..after 3000km, oil dropped again.. Stop, wait, start, pressure is better, but not perfect. I added one of those snake oil to restore oil pressure (rislone brand), pressure went back to normal. I was able to get to the 5000km mark... Got oil change done by a mechanic shop.

4 fresh oil, probably NAPA oil, NAPA filter.. Drove 4000km...no issue. Got oil changed by same shop

5 fresh oil, pressure is normal, drove 7000km (4500 miles). No issue.

6 changed oil, Castrol oil, FRAM filter.. After 1000km (600 miles), oil pressure went down to 0 again. At this point I'm blaming myself for using wrong brand of oil and filter.. So I change the oil..

7 I use napa oil and filter.. Tho this time oil pressure is lower than normal... I can drive for 45-60 minutes, then oil pressure drop to 0...I stop, let it sit for a bit, start and again I can drive for 45-60 min and pressure drop to 0 again.. And so on...

- I use 5w30 oil as recommended.

- I don't suspect the gauge to be wrong as when pressure get low, I can definitely hear the engine not getting oil

- there's no oil leak, not anywhere I park either

- I don't think I'm burning any oil, the oil level stay constant

- oil isn't milky.

- I did also check if the coolant was contaminated.. Negative.

- when I did the last oil change, I did pay attention to the oil coming out of the drain plug and towards the end, it did had a tiny bit of sludge in it. Very very little..

- I didn't experience any lost of power, when there's oil pressure.

I've searched the internet, asked many people.. But I get so many different diagnostic.

sefiroxx · May 13, 2020

Lots of possibilities.

- sludge in the pan might be blocking the intake. Drop pan.
- sludge in drain back cavities causing oil to pool up high. Should set low oil light. Next oil change, after drain, then car on (not start) and verify low oil signal comes on. If yes, go back to step one. If not, high pooling would result in or if slapping by the cams. Time for a sludge clean.
- sludge blocking oil pressure guage.

carkhz316 · May 13, 2020

I think assumptions are being made that it's literal oil pressure issues, and not something less serious. If you had 0 oil pressure, your motor would be clacking like hell. Unfortunately, the oil pressure gauge fails in the same matter as the rest of the stepper motor gauges in the '03+ trucks. I would verify the actual oil pressure before doing anything else.

txab · May 13, 2020

^^^^ This

newdude · May 13, 2020

11 hours ago, Jeff Dufour said:

Hi and thanks for reading. I hope I'm posting this in the right discussion.

I recently bought a used GMC Yukon xl 2004 and I have a strange oil pressure issue. Here's the story of my 7 oil change

1: bought truck, oil change was recent, drove about 5000km (3000 miles) pressure was normal and suddenly the oil pressure dropped, to zero. Checked oil level: normal.. Restarted truck: pressure ok.. I changed the oil.

2 fresh oil: Castrol and FRAM filter, drove about 4000km (2500 miles) again oil pressure dropped to 0...stop, wait restart, oil pressure isn't perfect, but enough to drive.. Did oil change..

3 fresh oil, Castrol and FRAM filter.. Pressure back to normal. Left for a long trip from west coast to the east coast..after 3000km, oil dropped again.. Stop, wait, start, pressure is better, but not perfect. I added one of those snake oil to restore oil pressure (rislone brand), pressure went back to normal. I was able to get to the 5000km mark... Got oil change done by a mechanic shop.

4 fresh oil, probably NAPA oil, NAPA filter.. Drove 4000km...no issue. Got oil changed by same shop

5 fresh oil, pressure is normal, drove 7000km (4500 miles). No issue.

6 changed oil, Castrol oil, FRAM filter.. After 1000km (600 miles), oil pressure went down to 0 again. At this point I'm blaming myself for using wrong brand of oil and filter.. So I change the oil..

7 I use napa oil and filter.. Tho this time oil pressure is lower than normal... I can drive for 45-60 minutes, then oil pressure drop to 0...I stop, let it sit for a bit, start and again I can drive for 45-60 min and pressure drop to 0 again.. And so on...

- I use 5w30 oil as recommended.

- I don't suspect the gauge to be wrong as when pressure get low, I can definitely hear the engine not getting oil

- there's no oil leak, not anywhere I park either

- I don't think I'm burning any oil, the oil level stay constant

- oil isn't milky.

- I did also check if the coolant was contaminated.. Negative.

- when I did the last oil change, I did pay attention to the oil coming out of the drain plug and towards the end, it did had a tiny bit of sludge in it. Very very little..

- I didn't experience any lost of power, when there's oil pressure.

I've searched the internet, asked many people.. But I get so many different diagnostic.

Have the oil pressure checked with an oil pressure test gauge. If you've got great oil pressure mechanically and verified with a test gauge, its quite possible that you need the cluster replaced/fixed as carkhz316 stated. If the pressure test matches what you've been seeing on the gauge, then you've got a mechanical issue.

Another strong possibility is the pickup tube o-ring. Fairly common on the Gen 3/Gen 4 LS/Vortec engines.

Also stick with ACDelco or NAPA/WIX filters.

Jeff Dufour · May 16, 2020

On 5/12/2020 at 11:22 PM, sefiroxx said:

Lots of possibilities.

- sludge in the pan might be blocking the intake. Drop pan.
- sludge in drain back cavities causing oil to pool up high. Should set low oil light. Next oil change, after drain, then car on (not start) and verify low oil signal comes on. If yes, go back to step one. If not, high pooling would result in or if slapping by the cams. Time for a sludge clean.
- sludge blocking oil pressure guage.

Thank you!

It was sludge or pick up O-ring

I dropped the pan, clean. So might as well change the O-ring...

Put new oil with seafoam. Drove for a bit and change oil again.

Pressure is back to normal!

Jeff Dufour · May 16, 2020

On 5/13/2020 at 7:13 AM, carkhz316 said:

I think assumptions are being made that it's literal oil pressure issues, and not something less serious. If you had 0 oil pressure, your motor would be clacking like hell. Unfortunately, the oil pressure gauge fails in the same matter as the rest of the stepper motor gauges in the '03+ trucks. I would verify the actual oil pressure before doing anything else.

As stated, when pressure was dropping, I was hearing the engine clacking. Hence why I wasn't suspecting a faulty gauge

carkhz316 · May 16, 2020

5 hours ago, Jeff Dufour said:

As stated, when pressure was dropping, I was hearing the engine clacking. Hence why I wasn't suspecting a faulty gauge

Sorry, I didn't see anything mentioned save for the ambiguous "definitely hear the engine not getting oil", whatever that was supposed to mean.

If you did indeed hear engine/ valvetrain noise in conjunction with your losses of oil pressure, then that would certainly suggest a oiling malfunction, whether it be due to the oil pump, pickup tube, or internal engine damage. I highly doubt the choice of oil, filter, or OCI have any bearing on it at this time, however.