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Discussion Starter · #1 · (Edited)
2012 Acura MDX with 120k miles, all the regular maintenance done since I bought it. It recently started making a loud whining/whirring upon starting (growing louder while accelerating). We did some research and thought it might be the power steering pump, so we replaced that and the o rings, and it’s still there. The alternator was replaced recently so I’m not sure if that is super relevant, but. Noise is coming from the passenger side of the engine bay.

Video of noise here

Thanks all …..update : after two separate Honda techs listened to it and said it was definitely the power steering pump, we had the tensioner pulley replaced and it fixed everything. Thanks all for your help!
 

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2008 MDX Tech+Power Tail Gate, Sterling Gray
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It sounds like the steering pump has air and the fluid is cavitating. I think sounds like low frequency pitch.

1. What work was done with the steering pump?
2. Was it replaced with a new one or refurbished?
3. Have you check all bearings including the serpentine tensioner bearings?
4. Have you done the timing belt and replaced the idle bearings?

Remove the serpentine and do a short engine run of about one minute start without the serpentine belt.
If the noise persists the problem is related to inner parts related to the timing belt.
If the noise is gone, then your problem is related to the outer parts related to the serpentine belt.
 

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It sounds like the steering pump has air and the fluid is cavitating. I think sounds like low frequency pitch.

1. What work was done with the steering pump?
2. Was it replaced with a new one or refurbished?
3. Have you check all bearings including the serpentine tensioner bearings?
4. Have you done the timing belt and replaced the idle bearings?

Remove the serpentine and do a short engine run of about one minute start without the serpentine belt.
If the noise persists the problem is related to inner parts related to the timing belt.
If the noise is gone, then your problem is related to the outer parts related to the serpentine belt.
1. Initially, the o-rings and fluid was changed.
2. Then the pump was replaced with a new one.
3. The pulleys are my next attempt, I haven’t checked or replaced those yet. To be honest, I’m not sure how to just check them.
4. I replaced the timing belt with the water pump about 15-20k ago, I don’t believe it came with an idler pulley.

That’s a good idea. I’ll try that next. Thanks.
 

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Did you flush and refilled with new PS fluid? Are you using Honda fluid?
That sound is identical to mine and I fixed by making sure there isn’t any air in the system. Did you turn the steering wheel side to side when flushing and refill?
 

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Did you flush and refilled with new PS fluid? Are you using Honda fluid?
That sound is identical to mine and I fixed by making sure there isn’t any air in the system. Did you turn the steering wheel side to side when flushing and refill?
Swaped orings, then pump, new fluid from Honda twice. Bled it multiple times. No change.
 

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started the engine without the serpentine belt and see you still have that noise or not. If you still have noise then it is coming from the timing belt area, bad water pump, idle pulley, oil pump and etc. now you have a time boom.
 

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Discussion Starter · #13 ·
started the engine without the serpentine belt and see you still have that noise or not. If you still have noise then it is coming from the timing belt area, bad water pump, idle pulley, oil pump and etc. now you have a time boom.
We pulled off the belt yesterday and started it without. The noise is completely gone with the belt off.
 

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We pulled off the belt yesterday and started it without. The noise is completely gone with the belt off.
That is good news. What about AC KOMPRESSOR or the alternator? Or serpentine belt pulley assembly?
If I were you I would be looking to replace the serpentine belt assembly first because it’s easier to replace and a lot cheaper than alternator or ac compressor
 

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Watch this. Could be a bad serpentine belt tensioner

 

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That is good news. What about AC KOMPRESSOR or the alternator? Or serpentine belt pulley assembly?
If I were you I would be looking to replace the serpentine belt assembly first because it’s easier to replace and a lot cheaper than alternator or ac compressor
I replaced the alternator last week, and both pulleys attached to the tensioner assembly spin freely and smoothly. I haven’t really looked into the AC much because it sounds like it’s coming from much higher up, but I’ll check into that next.
 

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eplaced the alternator last week, and both pulleys attached to the tensioner assembly spin freely and smoothly. I haven’t really looked into the AC much because it sounds like it’s coming from much higher up, but I’ll check into that next.
It is not about these two pulley. It is about the big spring inside the tensioner. It gets weak over time and loses its tension.
 
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