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Old 04-22-2012, 04:18 PM   #1
Scooby Newbie
Member#: 210295
Join Date: May 2009
Chapter/Region: NWIC
Default Humming noise on 03 WRX

This is hard to explain, so apologies for that.

My girlfriend informed me her 03 WRX (A/T) was making a humming noise and she thought it sounded like it was coming from the rear wheel well area. However sometimes it sounds like its coming from other places, its hard to pinpoint where.

She said the sound ONLY happens when she's been at a complete stop and presses the gas slightly, and at low speeds. If she steps on the gas firmly or doesn't come to a complete stop, there is no sound. Also, it does not happen every time. About 15-20% of the time maybe.

Today I drove it and was able to get the sound to happen. I came to a complete stop. Pressed the gas slightly and a humming noise started, hard to tell where it was coming from. It does kind of sound like the rear passenger side somewhere, but at the same time other places, very frustrating. I immediately put the car in neutral, took my foot of the gass, and just let it roll and the noise continued. As soon as I hit the brake, it stopped.

I was thinking fuel pump since its located back there and since it happens when the gas is pressed (albeit only when pressed slightly), however the noise continued even after I put the car in neutral and took my foot of the gas. And the fact the noise instantly stops when the brake is applied is weird to me. The brake fluid is fine. Pads and rotors fine also.

So in all, the noise does not increase or decrease in tone, pitch, or volume. Its a constant humming noise. I doesn't sound like it increases in speed with the speed of the car i.e. something spinning faster with the wheels. It only happens at low speeds and when barely pressing the gas. And goes away instantly when the brake is applied.

Any help is greatly appreciated. Its a weird noise to explain so I hope this makes sense.
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Old 04-23-2012, 08:01 AM   #2
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Member#: 30071
Join Date: Nov 2002
Chapter/Region: MAIC
Location: Northern Virginia
2001 RS-T
2015 XT


In some of the subaru's I've driven, the fuel pump is audibly noticeable while stopped. But that should be a steady hum versus the humming fluctuating.
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Old 04-24-2012, 11:26 AM   #3
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Join Date: May 2009
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The noise isn't happening while stopped though. If it is the fuel pump its tweaking out at weird times and is completely inaudible most of the time. That's why I'm confused.
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Old 04-25-2012, 12:08 PM   #4
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it could be the exhause lighting touching something
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Old 04-25-2012, 03:30 PM   #5
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Join Date: Jun 2006
Chapter/Region: MWSOC
Location: Michigan
02 Silver Wagon
"Stage 2"


Can you make a recording of it.

My first thought was wheel bearing, but your description seems to rule it out. It could be a CV axle, and it only makes noise when the suspension moves a certain way from hitting the gas or brakes.

If it really does not change as vehicles speed changes, it's nothing in the driveline. If it doesn't change pitch if you rev the engine a little, it's being caused by some other spinning motor, like the fuel pump.

The fuel pump does not run 100% all the time. The ECU will control the pump using PWM. So it could be that.
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