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View Full Version : Red Oil Pressure Light, but Oil Pressure is good



passatkid
02-27-2011, 03:42 PM
So, I have a 2001 Audi A4 Quatto Auto. This issue is that the oil pressure light come on when the car is up to temp and when ever you drop below 1500 rpms and then come back over 1500 RPMS. The light never comes on before the car is up to temp. Pressure hot idle is around 15psi, at 1500 rpms it is 25 psi and at 4k it is 50-60psi. I would say pressure is not the issue. So that leave the sender, not sure if its bad getting a new one. If that is not the issue I'm wondering what else it could be, possibly the cluster? If so hard is it to change the cluster with the immobilizer.

walky_talky20
02-27-2011, 07:14 PM
1. Is this a 1.8T? You didn't say.

2. 15 psi at hot idle is pretty dang low. And 60 psi at 4k when hot is also pretty low.

3. Absolute minimum spec oil pressure at hot idle is 1 bar or 14.5psi. For comparison, my 2001 1.8T makes about 26+ psi at hot idle, and 70+ psi at 3k. 4k is probably 80+, I'd have to check.

4. I'm guessing ND is North Dakota, USA? If so, your car does not have an immobilizer. Also, I don't think this has anything to do with your cluster.

5. Off the wall question of the day: Does your coolant temp gauge on the cluster read properly at all times? Oil temp gauge?

EDIT: fixed numbering. I'm an idiot, lol.

passatkid
02-28-2011, 05:36 AM
1. Yes 1.8T, previous owner said they replaced the oil pump and sensor due to the light then gave up on it and sold it.

5. Yes ND is North Dakota USA, the car is more like a 2001.5 as it is after the Vin split in 2001 if that matters.

6. Yes coolant temp gauge work just like it shoud, not sure about the oil temp due to the fact that I have not driven it that much.

Mr. Merk
02-28-2011, 05:59 AM
Had this on my wife's old 1.8T b5. We replaced the sender first, still came on. Turned out it was the oil pickup screen was full of sludge. Not a fun job.

Of course now that we sold the car we got a letter in the mail from Audi extending coverage for sludge up to 10yr 120,000mi

moshua
02-28-2011, 08:01 AM
I got my 97 aeb motor desludged and valve cover gasket replaced a while ago for same reason. I have never had the oil light come on again

sent from my Droid Incredible

passatkid
02-28-2011, 09:40 AM
The pump was replaced according to the previous owner, but I will look in to that. Also these cars run really high oil pressure.

walky_talky20
02-28-2011, 10:08 AM
Remember that our oil pressure switches don't close until the pressure gets up to 23psi. For this reason, the pressure switch is ignored by the cluster below 1500 RPM. BUT, if the pressure switch is open for even .5 seconds above 1500 rpm, it will trigger the oil pressure warning. Obviously the pressure decreases as the oil warms up (it thins out), so that is why you only have the issue when the engine is warm.

passatkid
02-28-2011, 10:49 AM
My next question is the switch simply a ground active switch, when the switch close is just cause continuy thought the switch so if you ground the oil pressure sensor wire the light should go off right?

Mr. Merk
02-28-2011, 11:37 AM
sure but its still not fixed

walky_talky20
02-28-2011, 12:18 PM
Yes, that is correct...while it is running. The cluster is smarter than that. If it sees the the pressure switch closed when the engine is OFF, then it will throw a continuous oil pressure warning (it realizes that the switch is stuck and will not give an accurate warning).

I suppose the real "Band-Aid" solution would be to install a pressure switch with a much lower threshold, like 5psi instead of the factory 17-23 psi. But I'd rather get the oil pressure within spec.

When hot, can you get the pressure to 100psi if you rev it to redline?

passatkid
02-28-2011, 12:54 PM
I don't know am not near the car at the moment, this weekend I will drop the pan and take a look. I have another pump that is new at the shop if I need. I was just asking about a switch so I understood how it worked.

walky_talky20
02-28-2011, 04:43 PM
Generally, the 1.8T's top end will start getting noisier once the oil pressure gets below 20psi or so.

Just checked my oil pressure after my drive home to be sure:
Idle: 26 psi
2k: 55 psi
3k: 70 psi
4k: 80 psi
5k: 95 psi

Mr. Merk
02-28-2011, 04:54 PM
Fyi: there is no just dropping the pan on a b5 1.8t. They suck. In a shop with a lift, air tools and a master tech it still took us 7 hours. The pump is probably fine. Its the pickup tube that you need.

walky_talky20
02-28-2011, 04:57 PM
Fyi: there is no just dropping the pan on a b5 1.8t. They suck. In a shop with a lift, air tools and a master tech it still took us 7 hours. The pump is probably fine. Its the pickup tube that you need.

^^ Yep. Big job. This is one of those jobs that you'd wish to combine with other things. Like a clutch job, or an engine build or some-such. Or at least a timing belt. I still can't believe why nobody has made an aftermarket 2 piece oil pan that makes this a 20 minute fix.

passatkid
03-01-2011, 05:48 AM
Generally, the 1.8T's top end will start getting noisier once the oil pressure gets below 20psi or so.

Just checked my oil pressure after my drive home to be sure:
Idle: 26 psi
2k: 55 psi
3k: 70 psi
4k: 80 psi
5k: 95 psi


Thanks, the car runs super smooth, no noise what so ever.

Fyi: there is no just dropping the pan on a b5 1.8t. They suck. In a shop with a lift, air tools and a master tech it still took us 7 hours. The pump is probably fine. Its the pickup tube that you need.

I'm an ex mechanic, I have tore a couple B5 passats to part them out. I can do a clutch in about 3 hours, I imagine I can do this in a day.

walky_talky20
03-01-2011, 10:18 AM
What weight oil are you running in this thing? Better yet, what exact oil?

passatkid
03-01-2011, 11:22 AM
Its either 0-30 or 0-40 Mobil1

DRock3d
03-01-2011, 01:24 PM
Fyi: there is no just dropping the pan on a b5 1.8t. They suck. In a shop with a lift, air tools and a master tech it still took us 7 hours. The pump is probably fine. Its the pickup tube that you need.

I was drunk, had hand tools, jackstands and a creeper and it probably took me 7 hours of actual work. What were you guys doing?

99blueb5
03-01-2011, 01:32 PM
i would say your hot idle pressure isnt that bad, when i was running 5-30 and at 220 oil temp at idle mine was around 15psi and it was fine no noise or anything, stepped up to a 5-40 and it went up to 20-25 at hot idle, my money is on the pickup is semi clogged, oil needs to be changed more frequently

Avant Nate
03-01-2011, 03:01 PM
Do you think kerosene would dissolve the sludge build up? One time I was changing oil and turbo, after emptying the oil, I put kero in though the turbo return line hole in the pan and let it soak overnight, emptied it and refilled the oil. That was a year ago.

A4Rob
03-01-2011, 03:51 PM
I was drunk, had hand tools, jackstands and a creeper and it probably took me 7 hours of actual work. What were you guys doing?

X2. 7 hours from a "master tech" seems a bit long. I did mine in about 6 hours in my garage... and I am not a mechanic by any means.

Mr. Merk
03-01-2011, 05:41 PM
I dunno. Maybe I was slowing him down. This also included my battling the bumper for the first time and cleaning the oil pickup and oilpan etc. Since tube that came with the pump was for a mk4.
Op: have you tried autorx yet?

We did that the first time the light was coming on intermittently and it was fine for a couple more years.

walky_talky20
03-01-2011, 08:34 PM
I would step up to a 40 weight oil (either Mobil 1 0w-40, or Castrol 5w-40 are easy to get), and see if that helps. You are really right on the edge for being in spec, so no damage is occurring - just the early warning. I'd run some AutoRX and up the oil weight and see if you can get it back to health, unless you don't mind dropping the pan. If you go with that method, I'd suggest installing a permanent oil pressure gauge in the interior so you can keep an eye on it. There is a possibility that the cleaner will make the problem worse before it gets better.

Nebone
03-01-2011, 08:41 PM
I get 20psi at hot idle using 5W40 Motul Oil viewed on a 0-80 psi VDI gage. Pickup was replaced last year.

stevejones19
03-01-2011, 09:47 PM
I would step up to a 40 weight oil (either Mobil 1 0w-40, or Castrol 5w-40 are easy to get), and see if that helps. You are really right on the edge for being in spec, so no damage is occurring - just the early warning. I'd run some AutoRX and up the oil weight and see if you can get it back to health, unless you don't mind dropping the pan. If you go with that method, I'd suggest installing a permanent oil pressure gauge in the interior so you can keep an eye on it. There is a possibility that the cleaner will make the problem worse before it gets better.


I'm gonna give this a shot if i keep my car much longer. What you said earlier describes what i have happening. No light when the car is warming up, but the minute i drive off it starts blinking sometimes. That and when i drive around a round-a-bout it will come on, even after checking the oil level. Glad i checked this thread out.

DRock3d
03-01-2011, 11:43 PM
I dunno. Maybe I was slowing him down. This also included my battling the bumper for the first time and cleaning the oil pickup and oilpan etc. Since tube that came with the pump was for a mk4.
Op: have you tried autorx yet?

We did that the first time the light was coming on intermittently and it was fine for a couple more years.

I see the problem, you put the car in service position. A real man just lifts it, drops the subframe, snub mount and pan. The only thing that should slow you down is the god damn bolts by the flywheel.

.Mad Hatter.
03-02-2011, 04:50 AM
I sit at 12psi all day long @ hot idle.

Motul X-cess 5W40

Mr. Merk
03-02-2011, 05:13 AM
I see the problem, you put the car in service position. A real man just lifts it, drops the subframe, snub mount and pan. The only thing that should slow you down is the god damn bolts by the flywheel.

yup, friggin service manual

passatkid
03-02-2011, 01:35 PM
FYI book time is 5.2 Hours, Warranty time is 4.9 hour according to the info I have. I will just pull it and look, I need to put motor mounts and control arm too, so I will do it all at the same time.

Mr. Merk
03-02-2011, 01:55 PM
yah perfect time to do it

audicribb
03-03-2011, 08:09 AM
Had the same problem turned out a glitch in my Apr 93 shut down my car somehow. The dealership found nothing mechanically wrong, sent the ecm to Apr, plugged it back in, and the car started and no light or problem. The car wouldnt even start up before. Was just a glitch in the software, but its fixed and running great.

passatkid
03-08-2011, 06:03 PM
Update, I didn't get my front end parts by the weekend, but I did take the oil pump pickup off. Some one had been in there before me. That said I clean the pan, pickup and reinstalled. I still get this damn light. It take alot longer but I still get it and it is very intermittent. Coolant and oil temp both at operating temp, and it seems to come on when slowing down right at 1500 rpms. Then when accelerating over 1500 rpms you don't get it.