Oil pressure issue

Hey tdi'ers
My new-to-me 98 jetta tdi flashed the oil light at me this morning. I pulled off and checked it, and it had the correct amount of oil, which I just put in 1500 miles ago or so, full syn 5w-40 Castrol which was supposed to meet 505.00

I restarted it and had no light, so I gingerly got back going and it seemed to be going fine, until I had to slow down a little, and at 2100 rpm, the light started flashing again, but I was accelerating and by the time I hit 2200 it went away.

After this, I watched closely for it and it didn't show up again for the rest of the 20 highway miles, but as I took the exit for work it beeped twice as I decelerated through 2000 rpm. As soon as I down shifted it went away.

I just had to replace the oil pressure sender on the filter housing because it had cracked and leaked oil.

I'm wondering if this is a known artifact, considering it is a very narrow rpm range? Or perhaps the first sign of a failing pump?

If it makes a difference, it's almost 100f out here.

Edit : 230k miles

I don't know if it is a known issue or not, but it should be reasonably easy to connect an oil pressure diagnostic tool to monitor actual pressure.

I have this one from Harbor Freight, and it seems to work well for me, though I've not yet had to use it on a VW.

https://www.harborfreight.com/Engine-Oil-Pressure-Test-Kit-62621.html

this has happened to me MANY TIMES, an air bubble or something gets in front of the transducer or its bad right off the shelf. #1 thing you should do before even driving it or spending any more $ is putting a oil psi gauge on it. you can easily plumb one on to the oil feed line to the turbo with a braided line to replace the hard line or where the transducer is now. either way, you want to verify that the oil is pumping around at a good psi. after that, you can mess with stuff and rest assured that no damage was done.
it should not matter even if its 120F outside, the oil is doing its job and cars would not last long if oil didnt work well on a 100*day

finally got a gauge on it.

hot:
idle was ~20psi
2000 rpm was around 40 psi
4000 rpm was around 60 psi.

seems like reasonable oil pressure.

I read how the sensor is just a ground path, and thought about how there was a bunch of oil on the connector from the sensor failure. so I brakleened it a bunch and it helped, but I still get the light and buzzer from time to time.

Mongler, how do you get rid of an air bubble? crack it while running for just a second?

I'm thinking of wiring the sensor wire directly to ground, and installing an oil pressure gauge... something this important shouldn't just be a light.

Sounds like you've an electrical problem.

A little air is just going to give you some damping. The light will stay on a fraction of a second longer at start and take a similar amount of extra time to go off when pressure drops. It won't cause a running engine to have momentary low readings.

I’ve had that happen before and it was due to a bad sensor.

It leaked oil through it when removed and tipped towards the ground.

Yup, given that the gauge reading proves the actual pressure is good (thank heavens) it's gonna be a sensor issue, or the wiring to the sensor.

Trick is, there's two... one's normally open and the other's normally closed, and they work at different pressures. Link above.

Abacus said:

I’ve had that happen before and it was due to a bad sensor.

Click to expand...

I had the gray one in the filter flange do the same. It left a huge trail of oil and wouldn’t always leak.... had me searching for a while. The little boot that covers it hid the source, but puked oil, when I pulled it off.

I don’t think I ever had warning lights, though. It worked, but just occasionally leaked oil.

-Todd

I had the same leak through the sensor on my 96 B4. It didn't cause any symptoms with the oil pressure light.

Vince Waldon said:

http://vincewaldon.com/index.php?option=com_content&task=view&id=40&Itemid=28

Click to expand...

Exactly the info I needed to diagnose. Thank you!