Oil Pressure light... can anything else be done?

[AudiHubby]

Hello All,

Here's everything I have done for my wife's 2004 A4 Cabriolet

NO OIL PRESSURE LIGHT
1) changed bad valve gasket and changed points, broke breather tubes in process.
2) changed bad tubes, seafoamed engine.
3) changed oil to Mobil 1 0w-30 with mobil 1 filter
LOW OIL PRESSURE LIGHT ON DOWN HILL DECELERATION
4) dropped pan, cleaned pan (desluged)
5) replaced oil pickup tube
6) Filled with Liqui-Moly 5W-30 and Maehl Filter
LOW OIL PRESSURE LIGHT ON DOWN HILL DECELERATION
7) Dropped pan again... wasn't dirty, but cleaned it again anyway
8) Replaced oil pump. Pickup was still spotless
9) Filled again with Liqui-Moly 5w-30
LOW OIL PRESSURE LIGHT ON DOWN HILL DECELERATION
10) Changed out pressure switch
11) Attached pressure test gauge
LOW OIL PRESSURE LIGHT ON DOWN HILL DECELERATION

OIL PRESSURE READINGS
---------------------
Cold idle ~60 psi
Cold 2k ~72 psi
Cold 3k ~87 psi

(after idling for 30 minutes)
Hot idle ~16 psi
Hot 2k ~41 psi
Hot 3k ~63 psi

(after driving 20 minutes [after the 30 minute idle])
Idle ~12 psi
2k ~40 psi
3k ~55 psi
5k ~70 psi

Other repairs made that had nothing to do with the oil line:
Timing belt changed
water pump changed
accessory belt changed
transmission fluid changed
Coolant flushed and refilled

At this point I have no idea on what else to do. Each time the oil was filled to the middle area on the dip stick.

We've had the car for about 8 months, the previous owner had taken pretty good care of it. We're at about 66,000 miles.

Any input appreciated.

Thanks!

Michael

[foley803]

Did you happen to take a look at the rod bearings while the pan was off?

[MikTip]

Black oil pressure switch

LED should light up at 1.2 to 1.6 bar
If LED does not light up:
Replace oil pressure switch.

Checking oil pressure
Disconnect wire from oil pressure switch.
Remove oil pressure switch and screw in oil pressure tester VAG1342 .
Screw oil pressure switch - 2 - into VAG1342 .
Start engine (engine oil temperature approx. 80 degree C).
Oil pressure at idling speed: 1.0 bar
Oil pressure at 3000 RPM: 3.5 to 4.5 bar
If readings do not match specifications:
Pressure relief valve or oil pump faulty, replace oil pump. Refer to Oil Pump .

Its either the oil (1)pressure warning switch,(2) the oil pressure relief valve or (3)the oil pump.
Test each to determine which one it is.

It could also be the J285 control module.

Got ross-tech vcds to read codes and scan control modules?

You wrote above you changed out the pressure switch? The oil pressure switch? Was your replacement OE Audi and new?

Youmentioned you removed sludge from you oil pan...how much sludge? Bad?

If you follow the factory repair manual it say the oil pressure relief valve might be bad.
If not that then the oil pump, if the relief and pressure switch is good.

I mentioned the control module as it gives you the light in your dash. Audi's are known for electrical gremlins....

My rh reverse light didnt work. Voltmeter said it was getting 8.4 volts. I trouble shot it down to the electrical control module under the dash. Change it, fixed the problem. Yet at no time did I get any sort of warning or did vcds pick it up!

[MikTip]

(after driving 20 minutes [after the 30 minute idle])
Idle ~12 psi
2k ~40 psi
3k ~55 psi
5k ~70 psi

1 bar = 14.50326 psi

Looking at your numbers above, 12psi is too low....

Try running Mobil 10w-40 Syntech.

Ive run it in my 2004 A4 1.8t for many years!

[AudiHubby]

Thank you gentlemen, both for your replies.

I'm thinking about the 5w-40, but have never considered the 10.

Black oil pressure switch



Its either the oil (1)pressure warning switch,(2) the oil pressure relief valve or (3)the oil pump.
Test each to determine which one it is.

I guess the last thing I would like to try is the oil pressure relief valve, but I have absolutely zero idea where that is located. Do you have a part number or know of any DIYs? And would that affect low oil pressure?

Thanks,

Michael

[AudiHubby]

Also my switch was new and OE.

And the sludge wasn't too bad. However, the original pickup tube was pretty gunky.

Thanks!

Michael

[AudiHubby]

Did you happen to take a look at the rod bearings while the pan was off?

Unfortunately I did not.

[walky_talky20]

Even when completely hot it should hit 70psi way before 5k. Mine holds 80psi+ at 3500 revs, all day. I run Rotella T6 5W-40. I really don't think 5W-30 would make that much difference, but I'd give 5 or 10w-40 a shot first before you tear into anything. The numbers aren't dangerously low. You might scrape by with some heavier oil.

[AudiHubby]

I've been looking at oil pressure relief valve stuff all day. Aside from taking the filter housing off and looking at the bearing and spring (which I'm not sure what to adjust when I get in there) I also found some people talking about this part Part #06A129101D. It's apparently located near the intake for the turbo.

Baffles me a lot. My pressure seems to start out strong. It's only after a long while that it seems to diminish. I can't imagine what else I can really do.does going to a 10w weight seem safe?

[walky_talky20]

In California? Yeah 10w-40 all year round should be fine. When it gets below freezing is when you may want to back it off to 5w-40 perhaps. Originally these engines called only for *w-40 oil. The manual stated that *w-30 oils were only to be run in the absence of available *w-40, and only for a short time at that. Since then there are now some 5w-30 oils that meet VW spec. But I prefer the 5w-40 myself, especially on a 1.8T with high miles.

[AudiHubby]

Bumpity Bump Bump, Bumpity Bump Bump, this thing's finally fixed!

[AudiHubby]

So after a long bit of research I finally figured out the problem (drum roll please) it was the breather system!

Through constant searching I found a video on youtube about that showed a guy removing the dipstick and it was making a terrible sucking sound and the engine was struggling. I decided (before I was going to flush my fresh 5w-30 and go to 5w-40) to try and pull mine out while it was running and the damn thing sounded like a jalopy.

After further research people recommended either the PCV or the PRV. I took of the PRV and did a test with suction and it seemed to be doing its job, so I removed the whole breather system (all the way down to the oil filter housing). The hoses were all new and not leaking. However I did have the original PCV/Bleeder combo. I looked longways down the T to see that the bleeder was slightly off center and wasn't holding a vacuum.

I replaced the PRV and PCV. The engine started up without issue, no suction in the crankcase, here were my readings.

--------------Cold Start-----------
........................Idle......2k.......3k
Old PCV/PRV 60 psi 72 psi 87 psi
New PCV/PRV 71 psi 80 psi 97 psi

------------------Hot--------------
........................Idle......2k.......3k
Old PCV/PRV 15 psi 50 psi 63 psi
New PCV/PRV 22 psi 64 psi 75 psi

I drove it for 30 minutes up and down hills, no light, ran great.

If I could do this all over again, this is what I would do. This is what I will do when I hit 100,000 (total cost of parts is about $170 if you go with OEM)

1) remove and clean valve cover
2) Seafoam engine (vacuum and crank)
3) replace all breather parts: PRV, PCV, and both breather hoses (part numbers at the bottom)
4) drain oil, replace old filter
5) Remove and de-sludge sump, replace pickup tube. Replace sump
6) fill with fresh oil (Synthetic of course)

Anyway, I hope this helps any weary searchers out there. I know it seems odd that vacuum issues might cause this. But if there is a lot of excess suction in the bottom end I imagine it would make it hard for oil to find its way up top.

I'd also like to point out that I was lucky enough to have a parts dealer here in Los Angeles that was able to help me out. If you need parts in a bind and can't wait for shipping, give ETY Parts a try in Eagle Rock.

Good luck fellow drivers!

Michael

Parts:
PRV Pressure Relief Valve (hockey puck): 06A129101D
Breather Hose (plastic piece of crap): 06B103213AK
PCV Pressure control Valve (Tee fittings): 06A103245F
Breather Hose Elbow (another plastic piece of crap): 06A103213AM (don't forget the o-ring)

Pics:
PRV Pressure Relief Valve (hockey puck): 06A129101D

Breather Hose (plastic piece of crap): 06B103213AK

PCV Pressure control Valve (Tee fittings): 06A103245F

Breather Hose Elbow (another plastic piece of crap): 06A103213AM (don't forget the o-ring)

[old guy]

Very interesting thread! Not something that I would ever have considered as a reason for the red low oil pressure light to come on. But after reading your symptoms it makes perfect sense. The PCV valve normally meters the amount of vacuum that gets pulled on the block. Apparently yours was broken and consequently was pulling the maximum amount of vacuum available from the intake manifold through the block rather than the normally metered amount. At idle this probably won't make much of a difference. But let’s consider what was happening when your light was coming on: "LOW OIL PRESSURE LIGHT ON DOWN HILL DECELERATION" from post #1.

Your motor was up to full operating temperature so the oil is thinned out. You are going downhill and off throttle. I assume your wife’s car is an automatic. This will put your motor under minimal load and consequently the oil pressure will be low from the lower motor speed. With the defective PCV your crankcase will be under maximum vacuum. Considerably more than at idle since the throttle plate will be closed and you are using the motor as a brake. Normally the PCV valve will meter the amount of vacuum being pulled on the block. I would guess that it would be no more than a few In-Hg. But with a defective PCV valve the amount would no longer be metered by the PCV. The motor will be pulling as much vacuum through the block as the PRV will allow. It could be as much as the typical manifold vacuum of 20 In-Hg. That means your oil pump will have to produce almost 10 psi more pressure to offset the increased crankcase vacuum in order to keep the low pressure oil light from coming on. As you already noted you were down to 15 psi at idle. Add a bit more crankcase vacuum from the motor braking and the red light comes on.

Definitely something I will store away for future diagnosticating. (pun intended)