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Discussion Starter #1
My 05 started to develop this high pitch noise whenever I turn it on. The noise is from the passenger side of the engine compartment. It is very high pitch and I can hear it from inside the house while the car is parked on the driveway with engine running idle. The noise the same at both idle and driving. Since it is from the drive belt area. I have taken the driving belt off to see if any of the accessories went wrong, and the noise was still the same even with the driving belt off. AC runs fine and the alternator seems to be good as well. I took a couple short videos, one with the belt on and the other with the belt off, to show the noise. I will post the videos once I figure out how to do it.

Any recommendations on what to do next to diagnose where the noise is from are greatly appreciated.
 

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Generally if there is a high pitch noise while in idle, it's caused by the idler pulley.

As for video, If you have a google account use it to create a YouTube account and upload your videos there and then link to them.
 

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Discussion Starter #3
Thanks Northof49. It happens as soon as the engine was turned on and goes away as soon as the engine was turned off. The noise is always there at both idle and driving.
 

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How many miles on your mdx? Have you done the timing belt job at 100k and 200k miles?

You can carefully look at the idler pully while the engine is running with a flashlight and see if it is wobbling... or any other pully.
 

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Discussion Starter #6
I took the driving belt off and then started the engine while putting the shift at 'park'. The noise was the same. This pretty much ruled out all the accessories on the drive belt as root cause.
 

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Bad water pump bearing and/or timing belt tensioner or idler pulley? The water pump is turned by the timing belt.

The fact that the noise happens with the accessory belt off indicates that it's not the power steering pump, alternator or A/C. Also won't be the accessory belt tensioner or idler pulley.
 

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I was thinking the same thing as rcy... I'm not sure you could use a mechanic's stethoscope to locate the sound if it's under the timing belt cover(s) but you just might find it somewhere else. They are cheap and easy to use, and something anyone who does ANY wrench twisting should have in their tool kit.

I helped a buddy troubleshoot an almost identical noise on his old Acura coupe. Turned out to be a bad radiator (electric) fan - the noise "echoed" off the engine, and it really seemed (for a second) to be coming out of the front of the motor.

Good luck...
 

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I suppose it could also be the crank pulley as that one turns off the engine and will still be spinning even with the accessory belt off. Maybe spray a bit of wd40 onto the crank pulley and see if the noise stops.
 

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The lubrication point for the crank pulley is pretty well shielded - you'll never get to it with WD-40. Remember that everything that's connected (driven by) the timing belt is also turning when the engine is running. That's most likely where you're going to find the problem. Good luck...
 

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Discussion Starter #11
Thanks guys. I took the recommendations from habbyguy and rcy trying to attack it this morning. When I started the engine, the outside temperature was about 45F and the noise was gone. It looks like it only shows up when the engine is hot. I am going to drive around and see what happens.
 

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Sounds like dry bearings making the noise.
If you don't want to spend the money on a steth, use a length of hose up against one ear and move it around to try and locate the general direction.
 

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Discussion Starter #13
After one and half days of testing, with much of a help from a close friend, I finally found out what caused the high pitch noise. It is from one of the intake manifold gaskets. The diagnosis tool I used include a $3 piece of hose to connect to the brake booster line and a crap 79 cents cigar. I opened the manifold and resit the gaskets. The noise was gone after that.
 
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