This is also known as sludging. VW has a bulletin regarding this problem which it blames on incorrect oil usage making sludge/carbon build up that clogs the pickup screen.
The bulletin tells you to pull the valve cover and inspect for carbon/sludge. This was an 01 Passat 1.8T with lifter noise on start up and oil pressure warn light comes on about a minute after starting.
Then you pull the cam caps and check for wear. On this car they were good, but I didn’t get a pic. I guess the theory here is they don’t have cam bearings so they will be the first part of the engine to take wear due to the low oil pressure. If the cam caps have wear they suggest replacing the engine.
Its a little difficult to pull the pan on a Passat…
After pulling the pan and finding more sludge I found the oil pickup tube/screen very clogged.
The entire PVC system was sludged up and that sludge could end up back in the pickup screen so you have to remove it and clean it or replace it. The oil filter housing needs to be removed and cleaned as well.
Here’s a sludged up PVC pipe.
Here’s the new pickup tube.
The bulletin wants you to pull the oil filter housing to clean out sludge. I pulled the intake to make it easy.
Here’s what the oil filter housing looked like.
If you ignore cleaning this out, the junk will fall out eventually and flow right into the oil pickup tube screen.
Here’s after I cleaned it. The valve cover and oil pan were this clean also but I didn’t get pics.