mystery solved

[Kim]

2000 996 Cab Tip / 105,000 miles:

Several weeks ago, my car began a loud squeal coming from the engine compartment almost every time I lifted my foot from the accelerator and slowed through about 30 mph. If I took pains to stop gently, it would continue at idle. If I stopped with a sudden stab of the brake pedal, it would cease. If I goosed the accelerator, it would cease.

After becoming silent at idle, I could restart the squeal by slowing increasing RPM to 1700 or so, then easing off the accelerator. Only happened after the car was warmed up.

Shortly after this started occurring, I noticed that the oil pressure would dive down in relation to how hard I was braking to a stop. If I coasted to a stop, the oil pressure settled at about 1/2 bar. If I braked firmly all the way to a stop, the oil pressure needle bounced off zero, momentarily triggering the oil warning light.

Took it to my friend / indy tech, who was quite puzzled at first. He used a stethoscope to eliminate, in his view, all the pulleys and the alternator as sources of the squeal. After I drove away, he did some research and phoned to ask me to return. With the engine running, he attempted to remove the oil filler cap. When he could not, he announced that he suspected the air / oil separator. It had failed, and was producing a stronger than normal negative pressure within the system. He offered that it could probably explain the oil pressure problems, also. After I left the car, he called again to explain he had discovered that replacing the AOS in a Tiptronic car would be considerably more labor than he had estimated.

While doing the work, he found oil fouling in the intakes to confirm his diagnosis.

Picked up the car this past weekend, and all is good. Squeal is gone, and oil pressure behaves normally, never diving with the brakes, and settling at 1.5 bar at idle.

One remaining problem: my oil quantity indicator on the dash has shown the crankcase to be empty for some time now. While under there, he replaced the oil quantity sender .... but the problem remains. Indicator does not appear to have failed .... still lights up prior to start, but shows zero oil. Any thoughts?

Kim

[ninsei]

cool. I wonder why a Tip would be more labor for that.

[Loren]

cool. I wonder why a Tip would be more labor for that.

The transmission has to come out to get to the oil separator on a Tip.