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Discussion Starter · #1 ·
My 2007 MDX has about 90k miles now and had the timing belt changed at a dealer about 3 years ago. Recently I can hear some noise from the front of the engine (pulley side). The noise is not heard when the gear selector is at 'Neutral'. It is very minimal when shifting into 'Park' and it will go away after I put it to 'Park' for a while. But it will show up right away when I put it in 'D' and hold the car still by braking.

So my conclusion is that it is a noise that is not related to transmission (due to location), just the engine itself. And it is only present when the engine is under load. I am really not sure whether it is due to a faulty belt or bearings in one of those pulleys. I have a few questions needing help.

1. Is it possible for a drive belt to make noise only when under load? I heard that typically a noisy belt would be at play at start up and it will go away after car is warmed up. But I have very limited experience. If a belt is able to generate noise only with load, I can replace the belt myself. Life is much easier that way.

2. I found a diagram for the pulley system for 1st MDX in the attachment. It should work for our MDX as well. It obviously is not due to AC pulley. So what is left is PS, Tensioner, Idler, Alternator and Crankshaft pulleys. Which one tends to make noise under load?

3. I actually bought a mechanic stethoscope and tried to listen to the pulleys. But it is quite dangerous to stick it around the spinning pulleys and belts. I shall try it again this coming weekend. If someone knows how to safely and accurately listen to those pulleys, please help me with some tips.

4. The only thing that might be related is that the noise happened shortly after I spilled some power steering fluid on the belt and possibly on the PS pulley (it might drip on other pulleys like tensioner, idler and crankshaft). I am not sure whether it is related or not. Can PS fluid damage belt or even the PS pulley?

This is the first thorny issue I came across myself. Any advice is greatly appreciated!
 

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Discussion Starter · #2 ·

This is a good video on diagnosing noise issues. It does seem that a contaminated belt has the potential to generate noise under load. But I am not sure that the noise can go away if I spray water on the belt, WHEN contaminated belt is the culprit?

Anyway, I probably will buy a new belt to try my luck. Suppose that I do not buy an OEM belt, these are available on rockauto. (See attachment.) Which belt is in general considered high quality belt?

Thanks a lot.
 

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Discussion Starter · #4 ·
i would start it up with no belt and see if the noise goes away This will give you a starting point if it goes away then you know its belt related if not then its else where
With the belt gone, only the crankshaft pulley will spin. So I can only rule out AC pulley and crankshaft pulley. How about the other 4? Thanks. I am a little puzzled. I know the noise will only show up with load. I am afraid I won't hear anything if I spin them by hand.
 
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