Oil pressure light issues

Hello everyone,
I have a 1999.5 TDI that I purchased bone stock and it had a couple issues that seem to be typical for my year including the hard starting when it's hot and the oil light coming on at higher RPMs. I did some deletes and sent out the ECU and got it redone with a stage 2 and that fixed the starting issue but the oil light still comes on periodically for no reason. I do have an oil pressure gauge that is connected to a T fitting that also has the sensor for the oil light connected to it as well. I did put a brand new sensor in it that is a genuine VW sensor from the dealer. I run Castrol 5W-40 full synthetic threw it. I'm running out of things to chase after and didn't know if anyone else has run into the same problem and figured out what to do. Thank you for your time, it's greatly appreciated!
Zack

What pressure are you reading on your gauge when the light comes on?

Normally it's when the oil pressure reaches the higher ranges after I first get on it once it's warmed up so anywhere between 70-85psi

Just to confirm then... your oil pressure light is coming on, with the engine hot, oil thin, RPMs up there, while you're seeing 70+ psi on the gauge?

If so, I'd probably shotgun the oil pressure sensor on the oil filter flange. It's cheap and if this was a wiring issue the light would be staying on all the time.

That said... I've never seen an older VW that can reach 70 psi when the engine is hot.

Well it is an electronic gauge and if I first start it and rev it a little it'll throw it up to 100. So idk how pin point accurate the gauge is but regardless of what it reads I have good pressure. But you're thinking I should try a different sensor? Are there different rated ones that I could try?

Well, 100 is TOO high... the pump has a pressure relief valve that's supposed to prevent it from getting that high.

So, you might want to try a different gauge at some point.

The main question is: do you have an actual oil pressure problem, or an electrical problem with the warning system?

The way to know is to measure the oil pressure with an accurate gauge and compare the oil pressure readings with what you'd expect from the sensor.

Here's a HOW-TO on how the oil pressure sensor system works and steps to diagnosis it further:

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

if everything else checks out (oil pump, pressure sensor, wiring) I would look at the oil pressure relief valve.

Internet guess- Engine has been run out of oil in the past and spun the bearings.
When this happened to me, installed new sensor, new pump, new rod and crank bearings finally cleared up the problem -just a guess.
If you do end up on this road, keep it mind, it's not especially hard to change out those bearings.

BobnOH said:

If you do end up on this road, keep it mind, it's not especially hard to change out those bearings.

Click to expand...

Have you done this with the engine and trans in the car?
I wondered about the pulley and flywheel seals leaking after the crank puts pressure on the bottom of them.
Add high mileage making the seals a bit harder with age.

wonneber said:

Have you done this with the engine and trans in the car?
I wondered about the pulley and flywheel seals leaking after the crank puts pressure on the bottom of them.
Add high mileage making the seals a bit harder with age.

Click to expand...

I have... you do 'em a couple bearing saddles at a time... all good.

To be clear: not a proper tear-down, definitely a band-aid, since you're not measuring elsewhere for engine wear etc etc etc. But it can be done.

Yes, not a proper tear-down as you say, not measuring anything. Just replacing the bearings one at a time. I have instructions sent from member QuickTD, if anyone is interested. I did need to dremil off a small bit of casting to get a socket on one of the caps. Mine were done at very low mileage and I wasn't concerned with wear. A bandaid if you will, but proper repair for the issue in that case. High mileage engine would warrant taking some measurements.

I remember there being 2 sensors. One at the back of the head for high pressure and the one on the pump for low pressure.
Maybe the high pressure sensor needs replaces or the pressure relief valve.