Author Topic: Weird car sound -- question for any home mechanics on here  (Read 2825 times)

brandino29

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Weird car sound -- question for any home mechanics on here
« on: January 28, 2015, 06:35:02 PM »
Trying to figure out what's going on with my car.  2005 Pontiac Vibe with 195k miles (I've only had it since 182k).  A few months ago I noticed as I was idling at a stoplight after having just gotten off the interstate a "thunk thunk thunk" sound.  I immediately worried it was an engine knock or something bound to cost way more than the car was worth so I pulled over and popped the hood and didn't hear it anywhere.  As I investigated more, I realized it was coming from "inside" the dashboard on the passenger side, kind of behind the glove box, but it was not audible from under the hood. 

Since it didn't seem to be running funny and it wasn't coming from the engine, I disregarded it and have driven it that way for a while, it's not noticeable when driving but as soon as you're idling you hear it, and it seems to be more noticeable after having been driven for a while at higher speeds (or it could just be that I'm more aware of it after the highway noise has died down).  Not so long ago, as I was trying to isolate the sound again, I discovered that it still occurs if the key in the ignition is turned to "on" but the car isn't running. (as in, past the point where you turn the key just to get the lights/radio on, and far enough to get the fan on, but not to actually turn the engine over). 

It makes a sort of low-key "thunk....thunk....thunk.............thunk...thunk..............thunk...thunk..." But it's not a clunking/knocking sound really (sounds are hard as hell to explain).

I have absolutely no idea what it is, but today it seemed to get much louder and 'move' more toward the center of the dashboard.  I'm wondering if it's just something to do with the fan for the cabin that's unimportant or if it's something that I need to get checked out pronto.

Thanks for any insights.   

coffeehound

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Re: Weird car sound -- question for any home mechanics on here
« Reply #1 on: January 28, 2015, 06:59:37 PM »
Raccoons?

lithy

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Re: Weird car sound -- question for any home mechanics on here
« Reply #2 on: January 28, 2015, 07:21:24 PM »
If its definitely coming from inside the dash and happens when the key is turned on but the car isn't running, that would suggest a part of the climate control system.  Sounds like it could be a failing blend door to me.  Its usually a plastic piece and if it hangs up, it can make a bit of a plastic knock. 

As for diagnosing it for sure.  Are you having any problems with heat or a/c?  Will it do it if you have the climate control off completely?  A stuck blend door will hang up on heat when you turn it to cool or vice versa.  If its knocking though it might be moving into place, just not smoothly so it could be hard to tell.  Depending on access, parts like this can be either a huge pain in the ass or a piece of cake to get to.  I would look up a How To, odds are you can at least see the part by removing something like the radio or the glove box.  You can then watch it and see if its operating normally.

choppingwood

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Re: Weird car sound -- question for any home mechanics on here
« Reply #3 on: January 28, 2015, 09:28:41 PM »
Last year, I had a dying Neon all year, and I found the best way to diagnose problems was to describe the noise or leak on Google search, and I would soon have a pretty good idea how much trouble the car was in. So, for example, I would Google "clunking noise behind glove compartment" or "clunking noise on passenger side when idling". Lots of times, the trouble wasn't serious and I could decide to ignore it. Other times, I found out I needed help quickly.


Greg

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Re: Weird car sound -- question for any home mechanics on here
« Reply #4 on: January 28, 2015, 09:50:39 PM »
Agree with lithy it might be a HVAC door motor or mechanism binding or stripped.  Also, could be antenna related, or possibly a vacuum controlled mechanism like a door lock?

brandino29

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Re: Weird car sound -- question for any home mechanics on here
« Reply #5 on: January 29, 2015, 08:44:28 AM »
It is most definitely coming from inside the dash, if I pop the hood I can't hear it, and it's most noticeable if I stick my head in the passenger leg area.  I haven't had any electrical problems, but now that I consider it, the A/C did start acting up in the late summer/early fall, blowing only mildly cool air when previously it was very cold -- I didn't worry much about it as the weather was cooling off and I didn't need A/C.  That could have happened around the time I first started noticing the sound.  Lately, I haven't been turning on the A/C, though usually I leave the defrost on because i like to have air flow in the car but not directly in my face from the vents.  It does seem to continue making the sound if I turn it completely off, but then again I can also still feel a little air flow even when the knob is all the way to off. 

It doesn't have one of those automatic antennas, and door locks/auto windows all seem to work fine. 


HairyUpperLip

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Re: Weird car sound -- question for any home mechanics on here
« Reply #6 on: January 29, 2015, 10:14:10 AM »
If you allow in fresh air, you will still feel air coming in.

If you choose to recirculate the air and turn it off completely, you shouldn't feel anything coming from the vents.
(I just googled this and according to the image I found this is the button under your AC button in the Vibe)

I also agree, it sounds like a HVAC issue especially because of the location of the sound.

Next time you are driving and you hear the sound, try turning off the heat/air completely. If the sound stops, then it's obviously related to the heating and air system. I'd personally also check if made a difference if I was using hot air or cold air.

The A/C issue you described sounds like you need to try recharging it first. Could be more, but either way A/C losing it's ability to cool shouldn't cause any sounds behind the dash.

PeachFuzzInVA

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Re: Weird car sound -- question for any home mechanics on here
« Reply #7 on: January 29, 2015, 12:35:11 PM »
I've seen this on a bunch of GM's from right around that era (never a Vibe). The blend door actuators are infamous on them for knocking just like what you're describing. It's a relatively inexpensive and easy replacement from what I recall.