Loosing oil pressure at Operating temp

**Hopsandirons** · 09-28-2024, 08:46 AM

I have a 2008 GMC Yukon XL Denali with the L92. 209k miles. When I start the car the oil pressure is great and runs around 50. But after it reaches operating temp the pressure slowly drops to zero and triggers alarms. I can turn the car off and start it again and the pressure jumps up to 30 or 40 and then slowly drops. I have verified the pressure is correct with a mechanical gauge and it matches the dash board.
I have also done the following.
New oil pump and new O ring
Replaced the cam shaft retainer plate
Replaced and cleaned out the sensor port to include filter.
No metal flakes on the oil plug and filter has no shavings when cut open
Prior to this issue I was having to add a about a quart of oil every 3 to 4 months. (I expect this from a high mileage motor)
Been using Amsoil for the last 3 years and changing oil ever 7500 miles.
No ticks or sounds from the engine when there is pressure but develops a tick when the pressure drops to zero.
My next thought was to run a BG engine flush and give a good cleaning and up the oil from 5w to a 10w. Also thinking about a piston upgrade since its cheaper than a new car.
Any other ideas or thoughts I would appreciate the help. Thanks

**Hopsandirons** · 10-14-2024, 03:35 PM

New symptoms I found today. With normal city driving and the RPM stays low 3k and below the oil pressure is staying right around 15. If the rpm is above 4k when speeding up on freeway when the motor returns to idle the pressure drops to zero and triggers alarms.

***SMWS6TA*** · 10-15-2024, 01:18 PM

I know you said you replaced the oil pump and o ring. Sometimes the o ring can get pinched or cut which will cause pressure issues.

Another item that can also cause pressure drop is the oil bar bell. if it's never been changed, that o ring could be a point of failure.

Next is blowby of piston rings, any smoke at idle or hard acceleration? With that many miles its possible the wear and tear has worn out the cylinders, rings or both.

I'm dealing with a simular issue with my L86 6.2L. It's lifter decided to

itself, The machine shop just got back with me that 3 of the cylinders are out of spec and need bore .005" over, the crank needs ground and polished, so +10 over bearings for mains and rods now are needed. Only good news was they were able to repair the lifter bore. So now I'm looking for pistons and bearings. Another $1300 to the build.