I have a high-pitched squeal coming from the turbo area of the engine bay. It starts at 2k rpm and stops when the rpms reach 3k. As the rpms drop it squeals again starting at 3k rpm and stops at 2k rpm. This happens both under load and when the car is not moving. Car has a stable idle at 700rpm when warmed up.

 

Turbo compressor wheel hitting the housing?

 

That’s what it sounds like to me to. I’d remove the intake pipes and check for shaft play.

 

That actually sounds air pump related. Try it with the air pump unplugged.

Dale

 

Airpump would be my guess too if you still have one. Unplug the connector and retest.

 

Thanks for the responses. Yup - it was the air pump. (Checked for play on turbos too and, fortunately, found none.)

Learning for the 100th time that where a high-pitched noise in a car appears to be coming from and where it is actually coming from may not be the same place.

Oddly, this is my second air pump to die. The previous one seized dramatically.

WTB: used air pump!

 

That was one ugly sound

 

Is your air pump pulling from atmosphere or from a filtered source? If you don't have a filter on the inlet pipe supposedly it kills the air pump quicker.

 

It was pulling through a filtered source. However, it was a used unit and I have no idea how many miles were on it.

 

Ditch the air pump and put a midpipe on it? Get an idler pulley instead....

 

Check my location!

 

oh bummer. Here in Texas we don't believe in no stinking emissions fancy pants stuff.

 

So, I finally got a new air pump installed (that turned out to be from an automatic FD, which is another story) and it had no effect. The noise was still there.

The noise did stop when the (new) air pump was disconnected so that pretty much left the ACV or the plumbing around it.

I found some old threads from 2007 and 2002 that described a similar sound from the ACV area. In general, it seems that the noise could be caused by a leak in ACV gasket or by the internal ACV wagonwheel check valve slipping out of place.

So I ordered a new ACV gasket (N3A4-13-996) and check valve (1480-13-730) and pulled the ACV (which involves pulling the UIM). I discovered that the gasket was fine and the check valve was in position (though I replaced them in any case).

However, I discovered that the air pump line LIM attachment flange was missing a bolt (lower left in picture below; the ACV, which bolts to the other side of the LIM, can be seen in the top of the picture). Either the bolt had slipped off since I bought the car (in 2004) or the previous owner had not put it back after some work way back in the day.

I replaced this bolt, reinstalled everything, and the noise disappeared! So, the noise was most likely caused by air escaping from the gasket between the air pump line and the LIM.