engine squeal
 

The car makes a strange continuous squeal/whistle while the engine is running. When the car was first purchased (1-2 months ago) the noise was there but only intermittently. The noise has no apparent effect on performance or mileage.

At first I suspected a belt problem but the noise is independent of acceleration, whereas it seems that the belt squeals most when accelerating.

I really have no idea what it is. It comes on when the car is turned on and stops when it is off. I am going to get it checked this week, but I want to have some idea of what it could be before I take it there.

Edit: I am going to check the fluid levels and whatnot tomorrow afternoon when I get out of class and it is bright outside. No puddles form under my car when I park it overnight, however.

Does the squeal vary in pitch or intensity? If so, when? Does it sound more like something rubbing or more like a whistle? Does it squeal when the car is stationary or just when moving (or vice versa)?

Things that can squeal:
Belts, Alternator, Water Pump, Air (smog) pump, Power Steering pump, timing belt rubbing something, Idle Speed Control motor (if your car uses one), maybe other items. Maybe some other electric motor under the hood? Fan for the heater/AC?

Things that can whistle:
Vacuum leak, air leak, exhaust leak.

These are things which have caused squeals and similar noises in cars I've owned over the years. Hopefully this will help you find your problem.

Others may have their own suggestions...

im leaning towards a vacuum leak. when the car is idling can you hear it? if so what area of the engine bay is it coming from?

so it squeals louder when you snap the throttle? what about when the engine is winding down? (after the snap)

still sounds like belt to me, check the belt, if its cracked, or shiney or really slick(kinda feels like a plastic layer os over the belt) then time to replace.

belt tensioner/idler pullies can squeal when the bearings are about to go out.

The sound varies in pitch but not intensity. The pitch becomes higher with higher RPMs. The sound deadens during engine braking but comes back when idling at the stop. As far as sound goes, it sounds more like a whistle than a squeal (I would think the sound of a belt sliding on a metal pulley at tension would be much, much louder).

I am going to check where the noise is coming from tomorrow afternoon, after I get out of class.

If it is a leak, how difficult is it to find/repair?

If it's a vacuum leak, one of the easiest ways to find it is to take a propane torch (DO NOT LIGHT IT) and crack it open, and wave it over all the vacuum lines and gasket areas you see. If you hit a leak it should increase your idle while you've got the propane over the leak.

A leak will usually be most prevalent when the engine is cold.

I know you think it sounds like it's coming from the engine compartment, but your description of varying pitch (based on engine RPM), fixed intensity, and off during engine braking (DFCO turns off the spark plugs too, right?) sounds like interference picked up by the radio.

Do you have power steering? If so, see if it changes much when you turn the wheels while parked.
You could also see if it changes much when you load the alternator (turn on all the lights and put the blower motor on hi).
How many miles does it have on it? If over 120K, it could be the timing belt tensioner or water pump bearing.

Get a long wooden handle and place one end on your ear and the other end on various components to see if you can narrow it down to something that's spinning. This won't work for a vacuum leak.

Some sort of bearing comes to mind with this...

I'd check the water pump, idler pullies, alternator, and lastly a/c pulley (bearings usually fail in that order). The water pump because it's under such a load all the time, the idlers because they spin quickly, alternator because it spins quickly but they usually build those bearings better and they end up replaced before bearings die, and the ac pulley last because, while it is possible, the pulley spins so slowly that the bearings don't get much of a chance to die. I've never seen it anyways.

I'm very sure the power steering won't do this as the bearings are actively lubricated with the power steering fluid.

If that isn't it you are looking at internal engine bearings and nobody likes those.

heh heh heh while you are at it check for loose battery connections to the engine, chassis and the battery terminals in case it is alternator noise. Take the alternator belt off and see if the sound stops when the engine is running - just don't run it too long since the water pump is not turning - it will probably be the water pump or alternator bearing since applying the brake loads the electrical system a little and the deceleration of the engine will change the load on the alternator bearings a little as the RPM drops it backloads the pulley on the alternator a little.