Hey all, I'm a long time lurker but given that searching yielded nothing that seemed to mirror my issue, I'm no a noob poster.
I have been having an issue with the oil dummy light coming on intermittently and rarely for about 6 months at this point. As a consequence of the first time, I immediately pulled over and checked the oil level (OK & Clean) and then had the car towed home just to be on the safe side.
Once at home, I tested the oil pressure with my home brewed VAG1342, both the pressure and the sensor checked out okay. Since the engine had no secondary symptoms of oil starvation (valve and bearing noise etc) I suspected a bad connection somewhere between the instrument cluster and the sensor so I put it all back together and resigned to trace down the electrical problem when I had more time to sort it out. with everything put back together, I started it up to warm the oil and move any crud I may have dislodged while messing with the oil pressure switch down into the filter, no oil pressure light. Feeling like this lent more credit to the theory of electrical issue, I changed the oil and filter, and replaced the switch with a new one (just to be on the safe side) and moved on with my day.
After that day, the problem occurred at random and checked out okay for another few weeks, each time resuming normal no light condition after the sensor was replaced. Concerned that it might just be crud in the oil pan intermittently clogging the pickup screen, I pulled the pan and inspected all of the pump connections and screen, all were remarkably clean and showed no signs of crud roaming around in the engine. Given that everything seemed to be checking out mechanically fine, I felt pretty confident that it was in fact an electrical issue. This car is after all no stranger to random electrical issues that seem to come and go with the wind.
Fast forward to a few weeks ago the light started to come on more and more frequently, so given that I had planned to have the car out of service for a week to rebuild the suspension and install a new timing belt I figured I'd check out the upper valvetrain to make sure that i didn't have any problems with the cam chain system and inspect for signs of sludge or other debris cruding things up, everything checked out remarkably clean and with little wear, which was to be expected in a car with 136K on the clock and religious 3-5000 mile oil changes with Mobil One 5-30 or 40 (winter/summer).
I got everything put back together and and started it up, runs smooth and quiet as always, but the oil light is now on constantly. So, I hook up the oil pressure gauge and double check that the pressure is fine and prepare to order an aftermarket pressure gauge but this time zero, zilch, nada. Absolutely no oil pressure... That can't be good... Given that I've never had an oil gauge stay at absolutely zero, I suspected the gauge took a crap on me so I pulled it apart, tested with pressurized air and it worked a-ok. So still doubting the probability of absolutely zero oil pressure, I pulled the sensor plug and cranked the engine over a couple times expecting oil to shoot out of the hole with great exuberance, nothing....
So, the question is, if you were betting people, and it wasn't your money, what would you bet on and why?
Given that the sensor port is the first stop after the oil pump, logic seems to suggest that the issue is likely to be an oil pump that is toast, but what I can't get past is that a) the problem has been intermittent b) up to this point the pump pressure has tested out okay and not given any indication of a weak pump, c) the engine has not demonstrated any other common symptoms of oil starvation (thank god) and d) I'm not really aware of any condition that could exist in an oil pump that would lead to both intermittent function AND absolute failure.
What are your thoughts.