Automotive

Front Hood Detective -- alternator, tensioner pulley or water pump?

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[OP]
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Jun 14, 2009
532 posts
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Toronto

Front Hood Detective -- alternator, tensioner pulley or water pump?

Guys

Just updating my previous thread that got me stumped and continues to get me stumped. It's about this intermittent whir sound that occurs from time to time. Unlike the last time where I thought it was a transmission related problem (as it occurred in live downtown traffic), this time I managed to pop up the hood in a quiet area and managed to still hear the sound after I reached my destination. I couldn't replicate it again when I got home, unfortunately... Vehicle involved: 2010 Acura RDX, 86000kms...

The sound emanates from somewhere where there's a serpentine belt spinning around the pulleys/alternator. At this point it could be either one of the few things but just venturing out a post to see what you guys think. It's an intermittent whir and doesnt occur all the time - the last time it happened was 2-3 weeks ago (which was also the first time it happened). Have driven ~1000kms since the last time it occured. My own research in youtube, internet, owners manual yields me some hypothesis:

a) Alternator -- all my research indicates that if it's the alternator giving out soon, the whirring sound is constant, not intermittent (?). HOWEVER, THE SOUND I HEAR FROM OTHER VEHICLES THAT HAVE SUCH ISSUE IS SIMILAR TO MINE (or at least close to it)... ALT nor Battery light isnt lit and certainly, power draw while using heater, radio, headlights doesnt change... Based on what I read if this is the part giving out, then these symptoms should be apparent? Maybe I should wait longer to see if the whirring sound becomes constant? (hence this is my #1 suspect, FWIW)

b) Tensioner pulleys -- the whirring sound does not sound like grinding nor bearings being crushed. But it still could be since it's within the area near the belt

c) Power Steering Pump -- It doesn't happen when I turn though, it also happens while I'm moving on stop go traffic at low speeds (at least that's when it happened the last time)

d) Water Pump -- no clue but maybe?

e) Serpentine Belt -- it is not a squealing high pitched sound but more a whir

Should you wait for whirring to occur constantly so that it's easier to diagnose when brought to the shop? or proactive replacement of all these above including serpentine belt since it'll probably dismantle everything? needless to say, it's a debate whether one does proactive replacement (but incorrect parts replaced and therefore problem unsolved since intermittent sound) or wait for constant whir sound (but then it might be too late and get stalled on the road)

FWIW- i called dealership to ask and obviously, the usual "we dont know we have to run computer tests/diagnostic from the service tech" etc etc... i mean, seriously? need to run diagnostic on what seems to be mechanical parts? does that make sense or is the vehicle that "technically advanced" LOL... (eg do you just want to charge me to run a diagnostic computer test)

Many thanks!
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Oct 14, 2010
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The fact that it is intermittent makes me think that it could be the AC compressor turning off and on. Your RDX has an automatic climate control system, and at this time of year the AC may be required periodically to maintain a comfortable cabin temperature.

Force the compressor to run by turning the temperature selector to the minimum setting. Check if the sound of the spinning compressor is the sound you are concerned about.
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eilrach wrote: ...
It's an intermittent whir and doesnt occur all the time - the last time it happened was 2-3 weeks ago (which was also the first time it happened). Have driven ~1000kms since the last time it occured. My own research in youtube, internet, owners manual yields me some hypothesis:
...
Sorry, but that's a bit confusing.

Are you worried about a noise that happened once.... 3 weeks ago... and it didn't happen again since?
[OP]
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Jun 14, 2009
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Toronto
motomondo wrote: Sorry, but that's a bit confusing.

Are you worried about a noise that happened once.... 3 weeks ago... and it didn't happen again since?
Yes motomondo, that whirring happened 3 weeks ago which was the first time it happened and I tried to replicate but couldnt (it disappeared as I was driving in stop go traffic downtown the first time it happened). Have been paying attention to it by not turning on heat, radio as I drive the past few weeks but didnt/couldnt hear anything...

It didnt/hasnt happened again till yesterday when I luckily was able to hear the sound as I was reaching my destination until I was in the parking lot and popped up the hood. Hence was able to know at least which area it came from. Did a bit of research on the net, viewed youtube videos etc and came with this post/thread here to see if you guys can help with the sleuthing


I tried to replicate it again today on two trips to and from the grocery today but unfortunately the sound wasnt there. I popped the hood in the garage this morning and when I got home - no sound, put on all the headlights, turned on heater, signal lights, radio etc, revved the engine, wipers turned on, turned on signals/hazards... all ok. (I'm trying to isolate the sound so that I can finally get at it -- eg find a proper fix, but I cant seem to replicate it so how to fix and hard to show/demonstrate to mechanic)
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Dec 28, 2007
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Alberta
If you're running the climate control in Auto, the AC compressor will come on to control the set temp even though you didn't manually turn it on. Watch the front of the AC compressor and see if the clutch engages.
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Apr 6, 2008
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Could it be the rad fan kicking on and off? It may only do it during certain temperatures, demand etc
Member
Oct 20, 2010
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i would suggest the power steering pump if it was the mdx(similar to the noise that comes from odysseys/pilots/ accords with the v6 engine)
[OP]
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Jun 14, 2009
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Toronto
Thanks bugsbunny. It might be even if my vehicle is not an mdx... what are the telltale signs if indeed that is breaking down? as mentioned it doesnt happen when i turn... from the forums ive read, and from general internet, it seems like if this is the culprit, it would be hard to steer? any other signs that would point to this as the culprit?

my rdx is a 4 banger turbo engine... however, not going to rule your suggestion out as indeed it's a honda... let me know if you have other thoughts. many thanks!

fwiw: i have checked the power steering fluid, not burnt smell, reddish tinge -- in fact, was planning a flush of it already until the sound went away... then now it's come back... and gone again, ~shrug~
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Feb 23, 2008
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Brampton
When it makes constant noise, remove the power steering belt. If the noise stops then you know it's the power steering.
Lets Go Blue Jays!!!
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Brampton
Use a stethoscope on the various parts to see which is making the noise. You can often hear a distinctly different noise from each part.
If you dont have one, a long ratchet extension held solidly to each part can work cupped to your ear.
Just be careful around moving parts.
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Oct 20, 2010
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eilrach wrote: Thanks bugsbunny. It might be even if my vehicle is not an mdx... what are the telltale signs if indeed that is breaking down? as mentioned it doesnt happen when i turn... from the forums ive read, and from general internet, it seems like if this is the culprit, it would be hard to steer? any other signs that would point to this as the culprit?

my rdx is a 4 banger turbo engine... however, not going to rule your suggestion out as indeed it's a honda... let me know if you have other thoughts. many thanks!

fwiw: i have checked the power steering fluid, not burnt smell, reddish tinge -- in fact, was planning a flush of it already until the sound went away... then now it's come back... and gone again, ~shrug~
when i had the Odyssey, initially, the noise was random, then was all the time, but mostly when turning. made more noise at slow speeds. After i replaced the power steering pump, it fixed the noise.
[OP]
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Jun 14, 2009
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Thanks bugsbunny, would you describe it more as a whirlwind or squeal or grind? Mine sounds like a whir versus the other two. So far I haven't isolated it other than the area I described. A bit hard when I tried using the screwdriver + open ended plastic container method esp now that it's not there again. Will record and upload video when I hear it again just to make this clearer for everyone wanting to help... (And hopefully to describe to the shop just in case it disappears again after I get a recording of it). So far, only happened 2x -- one three weeks ago, then last Friday... Nothing heard since driving on Saturday, yesterday or this morning...
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Jun 26, 2007
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???
No diagnostic scanner will be able to tell you a problem for these types of issues. There isn’t a sound sensor in the engine bay or any sensors on belts and pulleys.

Sometimes need to let the problem get worse or develop a pattern before you start fixing things as intermittent noise is difficult to diagnosis unless there’s a replicable pattern or condition.

If it’s a pulley issue then you’ll get it in the morning when everything is cold and it won’t come back till the next day. As the pulley spins the bearings inside start to heat up and the grease inside the bearing will get worked in. That’s when you know it’s a pulley issue.

A failing belt can be checked if you spray some lubricant on the belt and it stops squealing.
Sr. Member
Mar 17, 2006
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When you say a whir, do you mean like a supercharger? Not sure if your RDX has a timing chain (I think that year does), but it could be that. My car has been doing that whir sound as well ever since they changed my water pump (also does it when starting up the car first thing in the morning). The timing chain slipped a little while they replaced the pump and is probably a little too tight.
A whir (or whine) can be many things. Wheel bearing, alternator, timing chain, water pump a pulley bearing somewhere that's biting the dust. Don't obsess over something that happened once a few weeks ago. If it's anything, it will happen again. Trust me, most mechanical problems don't fix themselves. At one point it will get worse and come back more consistently. That's when you bring it in, get a proper diagnosis, and have it repaired.
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Oct 20, 2010
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This was the whine I got in my odyssey. After the 40sec mark.

Although more towards the time I replaced it. It wasnt as loud when it first came up.

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