Lost oil Pressure

**Skibum62** · 03-07-2021, 04:15 PM

Hi everyone! Hope everyone is doing ok.
I am new to this sight and am hoping for some advise. I am a hobby mechanic with basic skills and here is my story. I have a 2004 GTO with a stock 5.7. The car is garage kept with 100k miles. I lost oil pressure without hard driving or racing conditions. My son just started it one day and the check oil light came on. When he told me about the notice, I assumed it was the reminder for the oil change and was making no noise. After a couple hndered miles or so, I changed the oil. After completion, I realized it was due to no/low oil pressure and not the change reminder. Ironically, there was no rod knock or even upper end valve chatter. No brass or metal in the dirty oil, fyi. I changed the oil pressure switch with no change. I installed a mechanical guage at the pressure switch location and had zero oil pressure. I eventually got the oil pump off, what a PITA. I was hoping for a failed pump but there is no obvious damage. I blew 40 PSI of compressed air into the oil pump outlet/into the block, hoping to see pressure at the guage connected to the oil pressure switch. It still reads zero. I am assuming that the old pump is still good. Did I spin a bearing and lose my oil flow path?
Thank you in advance for any assistance.

***SMWS6TA*** · 03-08-2021, 11:01 AM

Roger I moved your thread to a section that will get more visibility.

***SMWS6TA*** · 03-08-2021, 11:09 AM

Have you cut open the oil filter and check for metal/bearing material?

No oil pressure after changing the OPSU and using a mechanical gauge leads me to believe:

There's an off chance it could be you pinched the o ring on the oil pick up tube or it's missing. But that means pulling the front cover again and verifying it's there or torn.

Oil Pump failure
Bearings are wiped
Oil Barbell is broken or lost it's o ring.
Or nightmare scenario - You could have what I had and had my block blew out internally and the oil is just flowing back in.

Either way it's looking like the only way to know is to pull the engine.

**Skibum62** · 03-09-2021, 03:55 AM

Thank you for the response. There is no metal in the filter and there was no metal in the oil. I am thinking that I spun a cam shaft bearing and was hoping to verify. If I cannot get compressed air through the block and tobtjebOPSI, what else could it be?

***SMWS6TA*** · 03-10-2021, 09:39 AM

The list i posted above.

Looks like you're going to have to pull the motor.

**Skibum62** · 04-12-2021, 03:26 PM

Hi everyone just an update. There is only so much inspection you can do without pulling the motor. I decided I would inspect the oil pump. After careful inspection and full comprehension on the design and operation, (clever and simple) I realized that the piston, (regulator) was sticking. You could see the scaring using an eye loop. I searched the internet for a failed ls1 pump and there are many examples. I replaced the pump without pulling the motor and had 35 psi using the starter and pulling the plugs. The regulator must have provided some lubrication occasionally. Bottom line is the car is back together, no knocks, runs good and has 50 psi of pressure. Hope this helps someone.
Good luck

***SMWS6TA*** · 04-12-2021, 08:46 PM

glad to hear. keep checking the filters for a few changes as well as the oil. Hopefully you got it before it could ear the bearings.

**desmond** · 05-19-2021, 02:29 PM

Originally Posted by Skibum62

Hi everyone just an update. There is only so much inspection you can do without pulling the motor. I decided I would inspect the oil pump. After careful inspection and full comprehension on the design and operation, (clever and simple) I realized that the piston, (regulator) was sticking. You could see the scaring using an eye loop. I searched the internet for a failed ls1 pump and there are many examples. I replaced the pump without pulling the motor and had 35 psi using the starter and pulling the plugs. The regulator must have provided some lubrication occasionally. Bottom line is the car is back together, no knocks, runs good and has 50 psi of pressure. Hope this helps someone.
Good luck

Great to hear you figured it out. My buddy is looking to get this GTO project with low oil pressure warning. Hope it doesn't have a knock. Just finishing the installation of the suspension from 4Wheelonline onto the truck this week before we can take a closer look at the GTO.