2000 MKIV Oil Light Flashing

[ajcook5]

Hey everyone, question for ya. My oil light came on and started flashing at me today. Oil level is good and it only comes on and flashes when I hit 2000rpm and then goes away after returning to idle. Oil changed 200 miles ago with Rotella T4 15w40. I would pressure test it but I don't currently have an oil pressure gauge. Has anyone had this issue? Common causes? Any input helps, thanks!

2000 MKIV Manual Jetta TDI 392k

 

[Vince Waldon]

Oil pressure is not monitored by the system below 2000 RPM, so that's why the light only comes on then.

Could be a sensor issue but could also be an actual pressure problem, so unless a visual inspection reveals an obvious broken wire at the sensor (side of the oil filter housing) the safe thing to do is to park the car until you can get a pressure gauge on it and figure out which bucket the problem is in.

That said, not uncommon for the sensor to fail and many folks just shot-gun it to see if that fixes the issue. The pump itself is pretty robust but the drive chain can break or the pickup clog.

If you *do* have low oil pressure the turbo life is measured in minutes, with the main bearings not much farther down the road.

 

[Midwesthick]

Silly question but was this before the motor being warmed up or was it cold outside?

In negative temps, I had mine come on and flash at me on the occasion. With my frostheater it never happened again.

 

[Sauaciden]

Silly question but was this before the motor being warmed up or was it cold outside?

In negative temps, I had mine come on and flash at me on the occasion. With my frostheater it never happened again.

It is possible that it depends on oil type. Never had oil light come on when using 5w40 during the winter (-25c)

 

[ajcook5]

Thanks for the input guys, this did happen when it was cold outside. I don't have an oil pressure tester readily available so I pulled the sensor and did a continuity / resistance test on it and it failed. Just installed the new one and seems to have fixed the issue. May do a pressure test on it anyway once I get my hands on the tester.

 

[Vince Waldon]

FWIW and just as a datapoint, I can't think of any reason why it would be normal for the oil light to come on with a cold but healthy engine. If anything the oil pressure will be the highest with the engine cold.... the oil is thicker and bearing clearances are smaller.

Edit: one reason does occur to me, at least an oil light during cranking a cold engine. VW's oil pressure warning system ignores oil pressure for the first 5-10 seconds of cranking and then engages. If for some reason the engine is still cranking at this point the oil pressure will be low (engine at 200-300RPM rather than idle) and the warning system will complain.

Still can't think of any routine reason for a low pressure light on a running cold engine though.

 

[ajcook5]

Update: car is running fine, no more oil light. Did an oil pressure test last night anyway, pressure fell within specs.

 

[paul_cat]

FWIW, you should be using Rotella T6, not T4. You need FULL synthetic 5W-40 to deal with turbo heat. 15W too heavy for an ALH...

 

[ajcook5]

FWIW, you should be using Rotella T6, not T4. You need FULL synthetic 5W-40 to deal with turbo heat. 15W too heavy for an ALH...

Noted, Thanks

 

[KLXD]

What's the difference between synthetic and full synthetic?

 

[ToxicDoc]

What's the difference between synthetic and full synthetic?

There are some synthetic blends that use regular oil mixed in.

 

[KLXD]

Then it wouldn't by synthetic it would be called synthetic blend like T5?

 

[ToxicDoc]

Then it wouldn't by synthetic it would be called synthetic blend like T5?

Correct. But someone new may not know there was a difference

 

[ghohouston]

I'll give my .02 on oil. I've ran regular dino 15w40 in my Alh since buying it with just over 200k miles. I'm at nearly 400k now, and absolutely no issues. Never had a turbo go out. Cam looked great when I swapped it out for a Stage 2 along with ported head. Now with the o.p. living in Wisconsin, I may not advise 15w40, but here in Texas, it has served me and my engine right, and will continue to do so.