I have a stock 2001 ls1 FBody. Engine was runni g great, besides leaking from the rear main seal. So, I replaced my rear main seal and cover, along with the oil pan gasket, new wix filter and 5w30 synthetic mobile 1.. now when the engine starts the oil pressure goes up to 35, and then dies down to zero in a matter of seconds. I turn it off and try it again and get the same reaults each time. Pressure goes up when I rev it, but goes back to zero at idle. And i can hear the lifters. I tried a mechanical gauge and get the same results...

 

Maybe when installing the oil pan gasket, the oil pickup got bent upward, causing the pressure to drop once the oil got sucked down.
A way to check that is add 2 more qts. of oil, and see if it still does it. If pressure stays up, that's what happened.
Just an idea...

 

Tried adding 2 more quarts and still no luck. Dripped the oil pan and everything looks fine.

 

None of these are going to be easy to check and I'm sorry in advance.

Where the oil pickup tube goes into the pump - do you know if it slipped out or if the o ring got pinched?

Where the barbell in the back goes in - did it get reinstalled correctly? Did you mess with the barbell at all?

Did anything get to partially blocking the holes in the pan the lead down to the filter?

 

I didn't mess with the barbell at all. But i went back outside and put in another 2 qts of oil and pressure is back to normal. So i'm guessing the pick up tube did get tweaked somehow. Going to pull the pan back off and take a look at the oring. As soon as it starts cooling down.

 

You probably are not going to like hearing this but I'll bet the rear cover is leaking oil pressure internally. There is a oil gallery passage in the upper rear cover, If the gasket is breached or wrong gasket etc it will dump all the oil right back down the rear cover into the pan. Good Luck.

 

Good ideas in here.

What I wonder about though is you said you tried extra oil and it didn't help. Then you said you dropped the pan everything looked okay and you added extra oil and the pressure was fine.

Did you run it on the regular amount of oil after dropping the pan the second time? How did it do? Or did you automatically over fill it and then check?

Between having the problem and not after you put it together the only thing that changed was you dropped the pan again. So what changed when you did that... that's the question that will lead to the answer to your problem.

If you didn't remove the pick up tube you shouldn't have o ring issues. It should be as it was before you took it apart. But checking the pickup tube is a good idea and if you go back in there replacing that o ring is a really good idea. Make sure you study up and use the right o ring depending on which pickup tube design you have.

 

The extra oil did help. Haven't had a chance to get back under the engine again. Gonna try to get to it this week.

 

I got a new pick up tube and it came with 2 different orings. One blue and one black. The one that came off looks grey. Just wondering which one I should use

 

Can't remember which color is which... but, if your pickup tube has a kind of "step" where the O-ring goes, use the thick one; if it's straight, use the thinner.

 

It's a melling 304s

 

That's what I was thinking.

 

So the extra oil didn't help and I assume the second sentence means you dropped the pan again and everything looked fine?

You just said it did help here but above you said it didn't help. I took this as meaning it helped after you dropped the pan again. Or did you not drop it again?? Or are you saying it's now 4 quarts over full?

If the extra oil fixed it it could be that something was up with the pickup or that you had aerated the oil pump and it needed to prime again and it was all a coincidental thing.

If the pressure is fine now, then it's likely not the barbell or the rear plate gasket. But hard to tell cause it's hard to understand what you're saying worked.

Have you tried running it again at the normal fill level yet?