Another squeaking/whining thread. . .

[john_Cramer]

2003 X5 3.0i with 107,000 miles

When driving at low speeds there are two whining sounds: one a lower pitch, low intensity whistling, and another higher frequency, higher intensity sound.

Taking the lower pitch sound first, it's fairly constant with road speed, does NOT vary with engine speed. Is not present at idle.

The higher pitch sound directly correlates with throttle pressure under load. Rolling at around 25 mph, press the gas, whining sound. Let off the gas, whine goes away. Put the car in neutral at the same road speed and gently rev the engine, no whining sound present.

I have removed and inspected the curved intake boot three times and I cannot find any cracks whatsoever, either in the big tube or the little one.

All of the standoffs for the various crankcase vent tubes are in place and there don't appear to be any cracks in the smaller vacuum hoses.

I have removed the ICV when it carboned up and stuck. This threw a code, so I pulled the ICV and cleaned it with throttle body cleaner until the vane rattled. I changed out the curved ICV boot that goes inside the intake manifold at this time. Cleared the code and no more ICV issues. Took the opportunity to inspect the intake boot, no cracks.

The DISA valve was chattering at idle, so I replaced that. No more chattering, but it didn't solve the whistle problem.

I pulled off the front wheels to verify that there was no metal-to-metal contact between the stoneguards and the rotor or wheel, and there's plenty of pad depth remaining.

I am thinking that the whine only when the throttle is on is diff noise. I have never changed either front, rear or transfer case fluid, I suppose I could pull the plugs and look for something abnormal.

I just do not think it's the intake boot: when the engine revs from idle the whistle is not present-- it is only present when the engine is under load, and stops when you take your foot off the gas.

I realize there are dozens of whining threads here, many of which never post a resolution, but before I start duct-taping microphones all over the car I thought I would offer this one up.

Thanks in advance for any assistance with this issue.