Hello everyone,

I was putting my newly-welded exhaust pipe back on last night (http://www.brickboard.com/AWD/volvo/1378155/V70/remove_exhaust_pipe_repair.html) and I heard a very strange noise that I wanted to ask about.

When I had everything back together I started the car while it was still up on the ramps so I could climb around underneath and listen and feel for problems before driving away.

While I was under there with the engine idling, I started to hear a high pitched whining noise. It was quiet at first and got loud very quickly, and stayed LOUD. Human ears aren't very good at distinguishing absolutes with volume, but I would say it seemed about as much louder than the engine as my microwave beep is over regular house noise (quiet radio, etc). It was constant and high pitched, and sort of like the noise you would hear from one of those high voltage transformers that are on the ground outside some large buildings.

Because I was already under the car I could easily hunt around to locate the noise. It seemed like it was coming from the oil filter (which I know is ridiculous, there is nothing to make noise in the oil filter... nonetheless, that's where it seemed to me the noise was coming from). I quickly got out from under the car to listen from other locations around the car and try to better triangulate the noise (ie: looking for height off the ground this time). It was definitely coming from the bottom of the engine, right where the oil filter was.

I checked to see if it was coming from the crank pulley - definitely not. I checked the AC compressor - definitely DEFINITELY not.

I felt around for vibrations but nothing seemed out of the ordinary (the engine /was/ idling).

I shut the car off, waited a moment (5 secs?) and turned it back on - the noise was gone.

My wife told me earlier in the day that she had heard a noise that matches with the one I heard, only a few days earlier (before I took the exhaust pipe off and disabled the car for the day :) )

I have only heard it the once, and my wife once as well.

The only thing I can think of that would be in that location that would make noise is the oil pump.

Does anyone have any ideas to add to this? It was a very disconcerting noise to be sure.

Has anyone ever replaced their oil pump? Mileage? Maintenance or failure? Are there signs of failure?