ferdas

Hi, I know this question have been asked many times but I got to the point where I don't know what to do next.
Red oil pressure light came up on my Audi A4. I dropped off the oil pan, cleaned pick up tube (not much on it), put new oil and filter, drove it for 20 min and light came up again. Ran oil/diesel mix for a few min to clean up everything. Dropped off the oil pan (nice and clean), replaced the pump (new one), checked for sludge - not bad, put the pan back. Removed valve cover - not bad again, replaced the pressure sensor (new one), put new oil 5w40 synthetic and filter, drove it and after 20min I got red light again. Checked the pressure with a manual gauge and this values: cold idle 65, warm idle 15, warm at 2k 30. The car is running fine no ticking or knocking noise. Since everything is replaced and clean what else could be wrong? Any ideas?

David.Norton

Hot pressure seems low, bearings? Since you are not knocking they may not be real worn, I'd pull the pan again, pull a few bearing caps, put some Plastigage in and check it.

ferdas

Thank you David for your replay. I don't have any experience with Plastigage so I will need to do some research first before I use it. Thanks again.

ferdas

I dropped off the pan and used green Plastigage and got 0.002 on each bearing cup. I did 2. So after reading other posts 0.002 sees to be fine. Do I need to check all bearings?

David.Norton

I'd check both a couple of rod bearings as well as a couple mains, but if they are close together and in spec I'd not bother with checking them all. I trust you also didn't see and scoring on the bearings. BTW I checked my book on the car, the 30 PSI is right at the bottom of the spec for pressure at 2K, which caused me to look at the oil weight specified, it says 20w50 for most operating temperatures, so I wonder if the problem is not just that the oil weight is to light at the 5w40.

ferdas

I replaced all rod and main bearings (they didn't look bad at all) but I did it anyway. Took the car for a drive and after 5.5 miles red light came again. I replaced everything what I think could be somehow related to low oil pressure and still getting red light. Tonight I removed oil filter housing and it looks clean. Running out of ideas what else could cause low pressure oil.

Anh Viet Vu

I have the same red oil warning light problem but on intermittently (check out my thread: https://www.audiworld.com/forums/a4-...8/low-2929323/). I was thinking of the bearings like uberwgn suggested but not sure. Did you have the light on just during brakes and right turns, or the light was on and stayed there unless you stopped and turned off engine?