Low oil pressure light c5 Allroad V8

[Alloutofdonuts]

This is not a drill. I’ve read thru many threads on the issue. Most point to a faulty oil pressure switch. Unfortunately for me rI’m pretty certain my car actually has a pressure issue. I’ve checked with a mechanical gauge; @idle it was around 20psi. @2krpm it’s around 30but revving up to maybe 3500-4500 it doesn’t move past 35psi. When I was checking oil pressure, the car started clacking(from the rear of the engine which I assume might be tensioners), also it started smoking pretty bad(blue and white).

My question is, how do you know if it’s the oil pump or the check valves or something else that needs to be replaced? At this point I’m wondering if I blew the HG/s while reving to check the pressure.

Backstory: the car is s 2004 Allroad V8. I bought it w/a rattle on start up, which was the cam adjuster gear and I replaced that with the updated JHM gear. The timing chain service had been done by the PO, but they opted not to do the adjusters.

Last year I didn’t register the car due to having another car(and ANOTHER project car - don’t we all). So it sat for about a year. I would run it every week and drive it around occasionally, at least once a month. About a month ago when it was idling the red oil pressure light comes on. After it had warmed up. I ran it until warm a few weeks ago. The light cam on again when it warmed up, but it sounded fine so I foolishly assumed it was ‘just the sensor’. Yesterday I replaced the sensor and even spliced in a section of wire(the wire had a nip in it from PO, also looked like the oil pressure switch was replaced recently). That made no difference. Today I hooked up a mechanical gauge and it has 25psi at idle. When reved to 2000 it goes up to about 30-35psi at best but not past that if it’s up to 4000. While I was doing that it started to smoke badly(blue and white) and at idle it started clacking coming from the back of the engine. The clacking goes away around 1500 which would kind of coincide with the chain tension era getting enough pressure? I’m afraid the engine has been damaged.

The next plan of attack is to drop the pan to see if the pickup tube is clogged, that’s the cheapest/easiest thing to do afaik. If the pickup is not clogged with crap, is there a way to tell if the pump is generating the correct pressure?

My guess as far as the oil pump vs check valves, is if it was the clogged check valves, it’d have HIGHER pressure, but if the oil psi switch is ‘above’ them then it’d read low, so I’m unsure how to determine if it’s the pump or not. The pump is $400, the check valve kit is $200. I’full replace what it needs, obviously I don’t want to wast the $ or time doing one or the other if it’s not necessary. Another complication is that I’m moving on the 21st. So this car has to either be fixed and running by then, or it’s going to the great Audi beyond!

Any suggestions would be very much appreciated. If my approach is flawed, I’ll take that too. I know I should’ve tested the pressure first, but it’s too late now.[/QUOTE]

[Alloutofdonuts]

No love for the V8 AR huh? lol me neither.

Dropped the pan thinking I’d find a bunch of crap in the screen but it was clean. In the pan there were some small bits of the old chain pads, and something resembling a nail. But there was also a bunch of grey sludge. Quite a bit in fact, I’d guess maybe 1/2-3/4 of a cup. I thought the oil looked sparkly when I drained it. I’m gonna venture a guess that the grey puke is aluminum from the pistons/bore??? Maybe that’s why it started smoking and clacking??? Has anyone else ever seen this or is it something else?

[Bordom]

Not too familiar with the chain motors, but on the belt versions the oil pressure sensor is located just off the passenger motor mount bracket and uses a generic VW pressure switch. I wouldn't be surprised if it's the same.

In my case, my sensor failed when driving and would come and go sporadically. I know it was done for sure when I had left the key on for a few mins and the low oil pressure warning popped up. It was really funny because the car was off with the key on lol.

You can give that a try and see what happens. Otherwise drop the pan like you said and check for debris, and while you're under there you can probably reach the oil pressure sensor. It's literally $10 but a bitch to reach