I've researched online and with several mechanics. Everyone is scratching their heads. Can anyone help?
I have a 1998 Passat GLX with the 2.8 V6 and a 5-speed trans. It has about 91,
000 miles and has had all regular and preventive maintenance performed without exception. The engine runs flawlessly with no obvious signs or sounds of problems. It starts, runs, and performs smoothly. The car looks and drives like it?s new.When the engine is hot (driving on a warm day and after at least 15 minutes of highway speed driving), the oil pressure warning light will come on and the alarm sounds when I ?hover? at 1600 RPM. The engine must be in a no-load situation. Meaning? If I?m accelerating or decelerating through 1600 RPM, I get no warning. But, if I?m hovering over that RPM for more than about 1 second, the light comes on. I can duplicate the problem at will. I get it EVERY time I hover at 1600. I've hovered at every 100 increments between 1000 and 2200 and I never get it at anything but 1600.
I can get the light to go off by either 1). Accelerating (loading the engine) and exceeding about 2,000 RPM (pushing in the clutch and getting the RPM above 2,000 does not reset the light. I must be driving and accelerating over
2,000) or 2). Restarting the engine.As long as I don?t hover over 1600 RPM, or the engine is not hot, there is no problem.
I've checked/done all the following: ?Oil Level ? good ?Oil weight and change history ? perfect. Never missed an oil change beyond
3, 500 miles. ?Filter ? using only VW recommended filters. ?Oil sensor switch ? replaced ? twice (both the ?blue? and ?white? switch) ?Tested/traced wiring from switch all the way to the panel. No indications of a problem, short, break. ?Pressure checked mechanically at, above, and below 2000 rpm. I?ve checked pressures in the shop and the mechanic has checked pressures driving. All gauge readings are within VW specs. ?I?ve run some Marvel Mystery Oil in the crankcase (most recent attempt) for about 1,000 miles to see if there was some sludge at pickup or a sticky oil pressure relief valve ? or just some other junk that might be causing the problem. No change.Thanks in advance for any help or advice. I'm willing to consider anything, but I can't replace the car right now.