No whining!
February 3, 2010 7:07 PM   Subscribe

Why would a car be making a high-pitched whining sound?

We just noticed that my husband's car (Subaru Impreza, 2004, 100K miles) is making a high-pitched whining/ringing noise. The thing is, it makes the noise when the engine is off. (It's been turned off for 2 hours now.) It sounds like it's coming from the engine. Also, when he uses the remote to unlock and lock the car, it kind of distorts the whining for a second (but it continues). Google is no help -- I keep finding results about cars making noises when they're actually being driven, but his car is just sitting there, doing nothing. Could it be the battery or something?
posted by trillian to Travel & Transportation (20 answers total)
Try disconnecting the battery.
posted by axiom at 7:13 PM on February 3, 2010

Response by poster: Can you tell where the sound is coming from?

Other than somewhere in the engine (?), we don't know -- the sound seems to fill up the whole garage.
posted by trillian at 7:14 PM on February 3, 2010

Before the whining started, did unlocked and locking the car beep the horn (with a remote, I mean). I don't know how car horns work, but it could be that.
posted by InsanePenguin at 7:14 PM on February 3, 2010

Hard to tell what it is from your description, but there are a number of electric devices that could do this; sometimes normally, sometimes not. Many cars have fans that run after they are shut off; that is normal; a fuel pump can have the type of high pitched whine you describe but should not be running with the ignition off unless a relay is stuck or something else is wrong. The list goes on and on. If you can open the hood and pinpoint the sound better it could narrow things down considerably.
posted by TedW at 7:14 PM on February 3, 2010

Have you had any belts replaced lately? Or are they still the originals.

How about your alternator? Is it the original or have you had recent work to it.

Bottom line, plan on getting it to the shop.
posted by lostinsupermarket at 7:14 PM on February 3, 2010

I meant to end that first sentence with a "?"
posted by InsanePenguin at 7:14 PM on February 3, 2010

Its the fan belt. I'm pretty sure it runs when the car's been off...the fan is supposed to cool. 2 hours after the car's not in use is pretty spectacular. Seems like its really not working, and thats why its still running 2 hours later.
posted by hal_c_on at 7:15 PM on February 3, 2010

Its the fan belt. I'm pretty sure it runs when the car's been off...the fan is supposed to cool. 2 hours after the car's not in use is pretty spectacular. Seems like its really not working, and thats why its still running 2 hours later.

I might agree with this diagnosis if and only if the whining continued when the car was on, but I figured trillian would mention that and she doesn't.
posted by InsanePenguin at 7:22 PM on February 3, 2010

Response by poster: OK... hmm, I guess it could be many things! I had been hoping there might be an answer like, "Oh, it's gotta be the [thing]." We'll call tomorrow morning.
posted by trillian at 7:26 PM on February 3, 2010

Fans that run when the car is off don't use belts - they're electric.
posted by davey_darling at 7:27 PM on February 3, 2010 [2 favorites]

I'd bet even money on some part of the stereo, horn, or alarm notification system. It's likely not major-mechanical if it's doing its thing for hours after the engine is turned off.

My Impreza's speakers made a wicked horrible whine for a while, even with the stereo off, until I found a fault in my new head unit installation.
posted by Netzapper at 7:31 PM on February 3, 2010

Fans that run when the car is off don't use belts - they're electric.

I don't know if this was pointed at me or not, but OH.
posted by InsanePenguin at 7:32 PM on February 3, 2010

This could be a bad fan relay or malfunctioning coolant temp sensor. Both of those could cause the fan to run for an extended (or indefinite) period of time after the vehicle has been shut off.
On all electric cooling fans, there's a big warning stating that the fans MAY TURN ON AT ANY TIME. This allows for whatever additional cooling may be necessary after the car has been shut off and power is available to the fans no matter what position the key is in.

Engines are vulnerable to heat soak or overheating after a drive since the water pump which circulates the coolant is mechanical and stops running when the engine stops running. Activating the electric fan can help mitigate the ill effects of heat soak.

There's also the possibility, if you have a turbocharged Impreza, that there's an after-run coolant pump incorporated into the cooling system. Turbos get extremely hot during normal operation and are even more susceptible to the ill effects of heat soak. I've seen a number of turbocharged motors on a variety of makes and models employ an electric after-run coolant pump to circulate coolant when the engine-driven coolant pump halts. I don't know the specifics of this pertaining to the Impreza off hand, but it wouldn't surprise me if this is the case.
posted by Jon-o at 8:20 PM on February 3, 2010

Tomorrow, park it outside so the sound doesn't echo in the garage before opening the hood and looking for the sound.
posted by davejay at 8:52 PM on February 3, 2010

Er, LISTENING for the sound.

listen -- do you smell something?
posted by davejay at 8:53 PM on February 3, 2010

My guess is that the trouble is somewhere in your cooling system. A fan slipping on a belt would explain the whining sound, and it would depend on your car whether or not that happens when the car is off (happens on our car). Do you have enough coolant? The answer might be as simple as a flush and fill.
posted by Gilbert at 11:26 PM on February 3, 2010

It could be that you have a vacuum problem in your cooling system and what you are hearing is your cooling system trying to replenish coolant from your resevoir through the secondary vacuum valve in that tank that is supposed to allow fluid to go back into your cooling system when it cools down.
Easy way to eliminate this as source: wait for your engine to cool down after you get home (15 minutes or so) Open the hood and loosen the radiator cap (hold a cloth over it when you do so in case it does send coolant out so you don't ruin your clothes) to see if that "releases" the vacuum and stops the noise -- if that stops the noise, you likely just have a "sticky" return valve and what you are hearing is the vacuum being "released" elsewhere in your cooling system through a hose or clamp where air is being "sucked" back into the cooling system (instead of cooling fluid from the tank) and making a whining noise.
Is your car running hot? That would indicate a lack of fluid, which would make sense - and is your resevoir at the "full cold" when cold? (if it is "higher," that would indicate fluid going into the tank, and not being sucked back in when it cools down)
If that doesn't do it -- my next guess is your battery -- is it a sealed battery or does it require water to be added - if so, check the level of water - the battery can be a source of gas which will build up and "release" if it isn't properly serviced with water.
posted by cactus86 at 11:30 AM on February 4, 2010

The fan belt does not run with the motor off.

FWIW, I am a mechanic.

Your car has an electric fan, which is not belt driven. That would be my first suspect. It is normal for it to run a for a few minutes (5-10) after the engine is turned off, but not longer than that. It's probably due to a faulty relay or sensor. By using the remote, it changes the pitch as the battery is being asked for more power, giving less to the fan. It will drain the battery eventually.
posted by peewinkle at 1:37 PM on February 4, 2010

I just had this same exact problem so hopefully this will save someone out there some aggravation. After 2 mechanics listened/looked briefly and were baffled, I finally took it to the dealer. Luckily someone had actually seen this problem before and my diag. time was only 30 minutes. Basically it is the keyless entry/alarm system buzzer. They didn't think it was something that would drain the battery but I didn't take any chances and just unhooked the battery. Part is around $50. I haven't had it replaced yet but don't think it is something that takes very long or is difficult. Guess it is located behind the grille.
The whine/buzzing comes from the front passenger engine area and seems difficult to pinpoint, like its moving around. You notice the pitch change a little when you use the remote to unlock the car. Apparently Subaru used a certain Alpine model that does not use the horn but instead uses a buzzer. I guess I never have changed any of my remote settings or whatever or maybe I would have heard that sound before and recognized it.
Hope this helps!
posted by lnovell at 8:15 PM on February 8, 2010

Sorry, but I just realized that when I lock/unlock my car, the sound is NOT a horn, it IS the buzzer thing. Just a couple of quick "beeps" BUT, it does not sound like the noise that was under the hood which was a constant drone. Looking back, I can definitely see that this is the same type of noise but there is really no way the average, non-tech person would be able to tell that they are related.
posted by lnovell at 8:22 PM on February 8, 2010

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