Oil pressure regulating valve

[Bayou Sailor]

Hey guys,
Being somewhat new to the A4, I have been looking at the MMI catalog to see what I might need for my now excellent running engine thanks to you guys, but I have a question. What in the heck is an Oil Pressure Regulating Valve? I've never heard of such.

[Dave Neptune]

It is basically a needle and seat only larger. The needle is spring loaded so that when the desired pressure is obtained from the oil pump the needle is moved off the seat to allow the "excess volume of oil" to pass back to the pan thus regulating the desired pressure to the rotating assembly. The "needle" is adjustable against a spring so tightening increases pressure and backing it out reduces it. Simple basic and reliable. It also regulates the oil temp to some extent.

Dave Neptune

[Al Schober]

It's a spring loaded relief valve.
There are two varieties. Early one uses a conical plug while the later one uses just a ball. For both the adjustment screw is on the manifold side, transmission end, just above the sump. Later model has the adjusting screw visible - loosen the locknut, adjust, tighten locknut. Early model the adjustment is hidden under an acorn nut. Both designs use a special design washer to seal the threads of the adjusting screw.
Oil pump is a gear pump - at a given RPM it will put out a fixed amount of oil. With new bearings in the engine, this oil pressure can get too high and cause erosion of the bearing metal. The relief valve limits the pressure, particularly at higher RPM.

[joe_db]

If your engine has a remote mount oil filter, that would usually have a pressure regulator as well.