Pulled it apart again. Checked the oil pump gears. There is some very light scoring on them. I mean, like you can see it but can't feel it with a fingernail when scraping across it. I can't imagine the pump is the problem. Pulled out the bypass valve and it looked fine. Also checked the "pressure relief valve" that's near the filter. I freaked out when I noticed there was no plunger in it. The RAVE sure shows a plunger. But I guess the relief valve is just for looks on the '04 or something. It was also missing from the old timing cover that I replaced. Who knew?
Anyway, put everything back together taking my time and making sure to do everything perfectly torqued. I even replaced the oil pickup o-ring this time.
Started it up and once it got hot......same problem. I've been driving it for a couple days now, keeping an eye on the mechanical gauge and revving it when it starts to drop below 10psi. It's acting like the bypass valve is opening up and getting stuck or something. I'm going to replace that next and see if it makes a difference. Good Times!

 

Wiser commentators may disagree but I think if you can't feel it with your fingernail it isn't there. I think that applies to EVERYTHING. And that certainly wouldn't be enough to affect oil pressure.

I think I commented earlier and I have replaced my scored timing cover (that would snag a fingernail, badly) with a smooth one and that fixed my pressure.

I guess your culprit is farther up or farther down. A bad o ring on the pickup tube or crack in the pickup tube. I think that was mentioned earlier and you checked. Farther up.. . I am trying to remember what seals oil to the crank (before it reaches the bearings) and what feeds the lifters. And drawing a blank. Someone else?

Also, I found the box for my humongous filter that fixed the problem temporarily with a badly scored pump: wix 51459. It is huge. It fits. It raises your pressure because it has probably three times the inside surface area. It hit all of the technical specs for our OEM filters almost perfectly. But that fixed a weak pump... That may not be your issue.

 

Did you ever solve this issue? I'm facing a very similar situation.

 

You may get a quicker response, if you PM him. He was logged on a week ago. But, he may miss your question...if he doesn't see this topic soon.

Brian.

 

Where did you hook up your mechanical gauge at?

 

At the oil pressure switch port. If I remember correctly, I also pulled a nearby plug from another port and got the same results.

 

I never did get a satisfactory solution to this issue. I couldn't afford coolant, oil, filter, gasket, o-rings, etc. to keep pulling it apart and putting it back together.
I did get a HUGE oil filter and that didn't seem to help much. I added some STP oil treatment to the 5w-40 Rotella to give a little more protection.
I put it back together and have done a few oil changes since and everything has been working just fine. If I idle for more than a few minutes, the oil pressure light comes on but a quick rev brings the pressure back up. I'm guessing it's my crank bearings but haven't had the gumption to get in and change those.
I don't go to drive-thru food places and I turn it off if I'm at a long red light. Seems to be working so far. It's been almost a year now and it's my daily driver.

 

do really mean 5w40 Rotella? Or is that a typo and you mean 15w40?

Thicker oil helps these engines.

 

Seriously?!? WOW.. what an about face! And here I thought I was doing it right all along I've been running 5W and 10W30 due to cold temps and I figured it helped keep things running when cold. SILLY me.. feeding it less than stellar oil when it deserves something better.

 

T6 is 5W40, T4 is 15W40

Either way, the viscosity is the same once they are up to temp.