Wolfie359

I've been getting a warning light for low oil pressure only when below 2000 RPM only once the oil has warmed up to around 100F to 150F for quite some time now. I never hear and tapping or have any other indication of oil starvation or other signs of low oil pressure.

Connected mechanical oil pressure test gauge and everything looked fine. Initial startup 60psi (Cold 60F), lowest it got at idle was about 25psi at about 140F. I replaced the oil pressure sensor located right next to the oil cooler & filter. Issue not resolved.

I've noticed my oil looks really milky and I have a lot of brownish white custard looking stuff on and around my oil cap. Did an oil system flush and changed oil. Same issue came back around 500 miles later.

Tested head gasket with blue fluid, found no indication of exhaust gasses in cooling system. Also have never found any traces of oil in cooling reservoir and not leaking or losing any coolant. Also not having any issues with temperature or overheating.

No signs of low compression or misfiring but have not tested compression, and no check engine light.

My problem seems to be too much moisture getting into the oil from somewhere causing the oil the loose viscosity and create a low oil pressure problem. After changing oil within 100 miles I got another low oil pressure warning and my oil is milky brown. My question is where the this moisture/water coming from? With oil pressure around 40-60psi and coolant pressure 20psi, its really hard to say its coolant getting into the oil without oil in cooling system. I haven't tested oil cooler but with no oil in coolant reservoir I don't suspect that's the issue. I also don't appear to be losing any coolant or oil... unless it mixing somewhere slowly just not showing up in coolant reservoir?

old96A4

I have the same motor in my 2003 a6. Mine does the samething onces in a while in the winter. Just change the oil and it should fix it. The problem is those engines have a venting problem. I guess ir has never been right. I've cleaned it out once before lasted for awhile. I see the stuff is back in the lines again. Not sure if you can fix it or not. For me it's only in the winter so i dkn't worry about. But when i getnthe low pressure thingncomibg on i just change the oil.

Hops

I know this is an old thread, but hey I was doing a search many years later and I ended up here. So hopefully this info may help others too.

A blocked PCV valve could be the cause of exhaust gas (including moisture therein) contaminating your oil in the crankcase. Replacing your PCV valve is a quick and easy DIY job.