My Disco has a high-pitched squeal on startup, until it gets warm. I knew it could be pretty much any pulley on the front of the engine, so I checked for play and found the tensioner pulley had some wobble. Replaced it only to start the car this morning and the squeal is still there. I haven't replaced the belt since I've owned the truck (3 mo's, 137k odo), so that's my next step, but there are some other factors that make me suspicious it's something else:

-I don't hear it right away when I start the engine, it takes probably 2-3 seconds once the engine is running to start.
-It doesn't seem to increase or decrease in pitch or volume based on engine rpm or load.
-When I shut the engine down, I realized this morning that I can still hear it for probably 5-10 seconds after shutdown.

The last one gives me the feeling it may be a a vacuum leak. I've been fortunate enough to never really have a belt go bad in one of my cars, so I'm not the most well-versed in what that sounds like, but it's definitely a different noise from what I've heard coming from other folks cars when they've clearly got a bad belt or pulley.

The noise in general is coming from the driver's side of the engine. I have a sneaking suspicion it's the vacuum line that runs to the brake booster, but I'm not entirely sure. Does this sound familiar to anyone? Is that what a vacuum leak sounds like? Am I just going crazy?

 

mine just started doing the same thing. sounds like its by the a/c compressor. be interested to see if anybodys got an answer. I'm at 182,000 miles