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2006 MDX, 140k miles - I was hearing a ticking noise coming from the pulleys when the engine was idling and under a load (when I turned the AC on), and at first thought there was an issue with the AC clutch. After digging around here and youtube (this guy had the EXACT same noise -
), it led me to believe it was a tension/idle pulley issue. I replaced the entire tensioner assembly (with 2 new pulleys on it), and the original noise seems to be gone, but now I have a new, louder rattle/ticking noise.

I made a couple videos of the new noise
1.
- Skip ahead to the 35 second mark to hear it more pronounced. When the cars not in gear (no load on engine), the rattle is very minimal. Once I put it in gear the noise gets louder, and if I lightly tap the gass it makes it rattle even louder (which you hear at the 35 second mark).

2.
- under the hood view. You can can hear it as soon as the video starts, but it's probably the most pronounced at the very end of the video. I take even the slightest tension off the belt (which you see in the video when I push the tensioner) the rattling noise stops.

any ideas what it could be?
 

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That's very much a dead ringer for a bad serpentine belt tensioner. Yes I read that you just did it. But that's exactly what they sound like when they go bad.

Good way to verify the tensioner? If it needs to warm up, then do so. Get it to the point where the engine running will make it happen. Shut off the engine. Now take your tensioner tool (I can see that you have one) and slowly increase and release tension. If you hear any creaking noise of any kind, then you have a binding bushing in the tensioner pivot and the assembly should be replaced. Again in your case.
 

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That's very much a dead ringer for a bad serpentine belt tensioner. Yes I read that you just did it. But that's exactly what they sound like when they go bad.

Good way to verify the tensioner? If it needs to warm up, then do so. Get it to the point where the engine running will make it happen. Shut off the engine. Now take your tensioner tool (I can see that you have one) and slowly increase and release tension. If you hear any creaking noise of any kind, then you have a binding bushing in the tensioner pivot and the assembly should be replaced. Again in your case.
thanks for the quick reply - it doesn't need to warm up to make the noise, makes it immediately when i turn the car on. I'm not hearing any creaking noises when I increase/release the tension, just that ticking noise.

just so I'm understanding you correctly, you're saying it's not one of the pulleys, but the brand new tensioner itself (which was just replaced)? is there any other way to troubleshoot it to isolate it to the tensioner to determine if I got a lemon?

I'll try to make another video - it's louder when it's in gear (foot on brake at a stop). just want to be sure it's that before I swap it out.
 

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here's another video where you can hear it crystal clear - it's in gear at the beginning of the video and making the noise. at about 10 second in, I shift to neutral and the sound gets much quieter, but can still be faintly heard, then shift back into gear at 18 seconds. at about 40 seconds into it I shift into park and the sound dissapears almost completely. then I shift back into gear at 52 second which starts it immediately, and then immediately turn the A/c on and it seems to stop. ac turned off 1:01 (car still in gear) and the noise comes back immediately. so it's only making noise when in gear at idle (and is the loudest) or in neutral

 

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I'm not hearing any creaking noises when I increase/release the tension, just that ticking noise.
But you do hear something when you try to move that tensioner back and forth? If so, bad tensioner.
 

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But if it isn't the tensioner and for sure the A/C compressor cycling on or off triggers the noise, then you're most likely looking into that compressor and or/compressor clutch.
 

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Discussion Starter #7
But if it isn't the tensioner and for sure the A/C compressor cycling on or off triggers the noise, then you're most likely looking into that compressor and or/compressor clutch.
shifting into gear seems to trigger it the worst, and then if I'm in gear and turn on the A/C (load on engine changes) it seems to disappear.

previously, just turning on the AC made noise (different noise, identical to the very first video I posted), which is why I replaced the tensioner in the first place. now, with the new tensioner the noise sounds different and is much louder, and turning on the AC actually makes it queieter
 

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Why don't you just take the belt off and see if the noise is still there. If it goes away then it's either that tensioner, the A/C or the alternator.

If it's still there, then it could be your P/S pump. Then take off the belt for the P/S pump to see if it goes away.

The MDX is nice that the water pump is driven by the timing belt, so you can run it for a while to listen to the noise without overheating your engine. However, don't run it too long like that since it will kill your battery.
 

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Why don't you just take the belt off and see if the noise is still there. If it goes away then it's either that tensioner, the A/C or the alternator.

If it's still there, then it could be your P/S pump. Then take off the belt for the P/S pump to see if it goes away.

The MDX is nice that the water pump is driven by the timing belt, so you can run it for a while to listen to the noise without overheating your engine. However, don't run it too long like that since it will kill your battery.
That's not going to help, the noise is only there when I put the car into gear at idle. While in gear (and making the noise), if I ever so slightly take the tension off with my serp belt tool, the noise stops. likewise, if I also turn the AC on (increasing the tension load) it stops as well. So it only is making the noise at a specific tension
 

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Discussion Starter #11
That's very much a dead ringer for a bad serpentine belt tensioner. Yes I read that you just did it. But that's exactly what they sound like when they go bad.

Good way to verify the tensioner? If it needs to warm up, then do so. Get it to the point where the engine running will make it happen. Shut off the engine. Now take your tensioner tool (I can see that you have one) and slowly increase and release tension. If you hear any creaking noise of any kind, then you have a binding bushing in the tensioner pivot and the assembly should be replaced. Again in your case.
Can't hear any creaking. Regardless, I went out this morning and replaced the entire tensioner again, same thing

 

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There's a VERY simple and cheap solution. Buy a mechanic's stethoscope, and poke around on the likely suspects when it's making the noise. The results will be obvious... when you put the rod on the noisy component, you're gonna know!

Search results for: 'stethoscope'
ordered one from amazon, but won't be here until tomorrow. how do you detect a bad bearing with the stethoscope (since the pulley's will be spinning)?
 

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You place the stethoscope's "probe" (basically, a metal rod) on the item you are checking. Obviously, you can't put it directly on a spinning pulley or bearing, but you can get close enough to discern the culprit. Put the probe on the power steering pump or alternator, and if the problem is one of those bearings going out, you'll clearly hear the noise through the pump/alternator housing. Same with the A/C compressor. You could put the probe on the belt tensioner's housing (between the two pulleys), though I would guess it's safe to rule that out at this point. Not too many other things can be causing the noise, IMHO...

I just now listened to the video clip, and would suggest that it might have nothing to do with the belt (or anything connected to it)... It could be a motor mount, or some other barely-touching metal to metal item. The good news is, that stethoscope will still help you chase it down... the louder the noise is through the stethoscope, the closer you are to the source of that noise.
 

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You place the stethoscope's "probe" (basically, a metal rod) on the item you are checking. Obviously, you can't put it directly on a spinning pulley or bearing, but you can get close enough to discern the culprit. Put the probe on the power steering pump or alternator, and if the problem is one of those bearings going out, you'll clearly hear the noise through the pump/alternator housing. Same with the A/C compressor. You could put the probe on the belt tensioner's housing (between the two pulleys), though I would guess it's safe to rule that out at this point. Not too many other things can be causing the noise, IMHO...

I just now listened to the video clip, and would suggest that it might have nothing to do with the belt (or anything connected to it)... It could be a motor mount, or some other barely-touching metal to metal item. The good news is, that stethoscope will still help you chase it down... the louder the noise is through the stethoscope, the closer you are to the source of that noise.
stethoscope showed up today and I gave it a try - no sure exactly what type of sound I should be listening for. Everythings loud, so I dont know what a 'normal' sound is versus a 'not-normal' sound is. I put the probe on the AC clutch (AC was off), and it sounded a little rough (whereas the alternator pulley was much louder, but smoother), but I don't know if the AC clutch sound was bad or not.
 

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Discussion Starter #15
first, took the serp belt off all together and ran the engine, shifted into gear, etc and no noise whatsoever, so it's definitely gotta be something driven from the belt.

I went ahead and replaced the AC clutch and bearing, since the noise seemed to be coming from there based on my novice stethoscope skills. unfortunately that made no difference so it looks like that's not the culprit.

my next guess, since the noise definitely seems to be in that area, is to replace the alternator again. I put one in less than a year ago, maybe the bearing in it is bad - at least that's my only guess now, as I'm pulling my hair out trying to figure out what the issue is
 

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Spin the alternator by hand to see if it makes any squeaking or rubbing noise.

Since you replaced the alternator last year, that's what I would suspect, unless you replaced it with a brand new one from Honda.

The people who rebuilt alternators are really cheesy folks. They would pry the seals off the bearings and pack it with grease instead of putting in a new bearing. When they do put in a new bearing, it is always one of those dime-a-dozen bearing from China.

I have had rebuilt alternator that lasts no more than a year or two. When they start making noise, it is invariably the front bearing.

You can take the alternator apart and replace the front bearing yourself. It's really easy to do. The size is 6303 if my memory serves.

http://www.amazon.com/6303-2NSE9-bearing-6303-2NSE-6303-2RS-bearings/dp/B018B2GVRE?ie=UTF8&keywords=6303 nachi&qid=1465348880&ref_=sr_1_4&s=industrial&sr=1-4

Good luck
 

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I replaced the entire alternator (lifetime warranty, so it didn't cost me anything), and still didn't fix it. On a whim, I put the original tensioner (the part I replaced twice) back in and the noise was back to how it initially was, a minor rattle. So I took a closer look at the aftermarket replacement tensioner assembly I was trying to replace it with (Dayco Noslack), and it looks like it wasn't identical to the OEM one, specifically the arm on it (with tensioner pulley) it was thicker and thereby decreasing the gap between the arm and the water pump cover. I'll try to get a picture of it to illustrate what I'm talking about. So now I'm back to square one, with a new clutch bearing, new alternator, and the original factory tensioner. Now I'm debating on whether to pony up the $150 for a Honda tensioner from the dealer to see if that fixes it, or just surrender and take it in to be diagnosed. Aside from the tensioner, any other ideas what the cause could be? The mount that's right beside the belt is good, so it's not that. the noise definitely seems to be most pronounced in the area around the tensioner/alternator/compressor, but again all 3 have been replaced, but the new aftermaket tensioner seems to have caused an even louder noise when it was in
 

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Don't give up yet. If my memory serves, the tensioner pulley has a replaceable bearing size 6303-2RS (2RS=rubber seal on both sides). Just order that and knock out the old bearing, heat up the pulley with a heat gun to about 160F then drop the new bearing in. If you heat up the pulley first, it makes it easier to drive the new bearing in.

I used the Japanese made Nachi 6303-NSE (same as the -2RS) on amazon, which costs less than $10. There is no need for an entire new tensioner.

However, take out the old tensioner first and read the bearing number from there since my memory could be faulty regarding the bearing part number.

Beware that the pulley is held by a bolt with LH thread, so you have to turn clockwise to remove that bolt.

I have a 2001 MDX with only one pulley, but your model year might have two pulleys instead.

Good luck.
 

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Don't give up yet. If my memory serves, the tensioner pulley has a replaceable bearing size 6303-2RS (2RS=rubber seal on both sides). Just order that and knock out the old bearing, heat up the pulley with a heat gun to about 160F then drop the new bearing in. If you heat up the pulley first, it makes it easier to drive the new bearing in.

I used the Japanese made Nachi 6303-NSE (same as the -2RS) on amazon, which costs less than $10. There is no need for an entire new tensioner.

However, take out the old tensioner first and read the bearing number from there since my memory could be faulty regarding the bearing part number.

Beware that the pulley is held by a bolt with LH thread, so you have to turn clockwise to remove that bolt.

I have a 2001 MDX with only one pulley, but your model year might have two pulleys instead.

Good luck.
I actually already did that - currently the original factory tensioner body has 2 new pulleys off the (aftermarket) tensioner I bought. I was trying to isolate the issue. Based on that, the noise is how it originally was, so if the root issue is indeed tensioner related, than its due to the tensioner body and not either of the pulleys on it
 

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I just realized something. Certain model years (say around the mid-2000s), have a situation where the replacement tensioners interfere with a strengthening rib on the lower timing belt cover. The retrofit is to cut/grind away the rib before installing the new tensioner.
 
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