Weird Humming Noise

[Buckles]

Little bit of background first. I purchased my 06 SR5 in July of last year. It had 73k on it when I bought it, and it now has 85k.

Recently it has developed a very strange humming noise. I first noticed it in February after eating out with my family for a birthday dinner. Truck ran fine all day, then I started it up after dinner and it had a strange humming noise coming from the engine bay. It hummed at idle, and seemed to get louder/high pitched until about 40 mph then it would disappear. As soon as I slowed down, it would come back. I pulled over and opened up the hood and didnt see anything out of place. I let it sit for about 15 minutes then started it up again. The noise was gone. That was the last I heard of it.

Fast forward to today. I went out to lunch with a coworker. We were sitting at a stoplight and I heard the noise again. At first I thought it was either the semi truck next to me or the construction workers on the street corner.
I was in a turn lane, and as I started to turn my wheel (while sitting still) the hum got louder. As I pulled away I realized the noise was coming from my car. We grabbed lunch then stopped at Buccee's for a drink. It made the noise all the way until we left Buccee's, then it just stopped.

The truck seems to be running fine aside from the noise. Idle is smooth and RPMs are where they should be. I dont ever see a spike in RPMs while I hear the noise.

Anyone have any ideas whats causing this? My first thought it a vacuum leak, but I have no idea where to even start.

 

[preacher35]

Man, that could be so many things. You didn't mention whether you have a V6 or V8. Did it make the humming sound when it was in neutral and/or park, or only when in drive? You mentioned that it would get worse when you would turn the steering wheel. I suppose for starters, I would take a look at your power steering reservoir and make sure it is topped off. Then I would take a look at the serpentine belt and water pump. Hopefully BlackWorksInc will see your post and speculate as he is a Toyota service tech and know his stuff way better than myself.

 

[Buckles]

Sorry. Forgot to mention it is a V6 and it does make the noise in neutral and park.

Last time I went for an oil change the guy did try to tell me that the power steering fluid smelled burnt, but I was in a hurry and just figured he was trying to sell me stuff.

 

[galactic_04]

get a stethoscope and listen around. Could be power steering pump, water pump (watch your coolant level), alternator, etc...

 

[Buckles]

Coolant seems to be ok. I added some about 2 months ago and it has stayed the same since.

 

[bwake21]

I am having a similar issue, mine seems to show up randomly when driving, starting up etc. But, I have narrowed it down (I think) to a steering issue as I can recreate the hum with the wheel at full crank, both ways.

PS fluid level is spot on, no discoloration.
No trouble/difficulty turning.
RPM/Temp fine.

I am thinking about replacing the PS pump but would like to see if anyone has found the cause yet.

 

[Buckles]

Well I haven't had it happen since again since I originally posted this. Still not sure what caused it though.

 

[lunchindabox]

... At first I thought it was either the semi truck next to me or the construction workers on the street corner.
I was in a turn lane, and as I started to turn my wheel (while sitting still) the hum got louder. As I pulled away I realized the noise was coming from my car.

Sounds like you got yoru answer right there homie. Maybe the pulley or the pump or the belt. I'd start there.

 

[anidejoha]

What happened to this sound?

Hey guys, I'm experiencing the same exact sound in my 97 V6 limited. Hums at idle, also when in park, but as soon as I get above 20 mph it goes away. It's not a steady sound when in idle, the intensity of the sound goes up and down when in idle at for example a red light. I just changed the water pump and belts. Had it at two different mechanics who couldn't pin point the sound, but mentioned something about the PS pump... Engine runs smoothly though. Any suggestions? Did anyone mechanically solve this problem, or did it just go away?

 

[Go-Fast Boat]

Also have a similar issue with a '97 Limited. Low humming noise at idle. Noise goes away the second I step on the gas to accelerate. I'm thinking PS pump, although fluid level/color is good and steering feels perfectly normal. My fear is an oil pump...

 

[mjlmjl]

Hi,

OK - so I'll jump on the band wagon too - with a humming noise.

In my case, the noise seems to come behind the brake pedal area in the engine compartment area.

The "pitch" of the noise seems to vary with the speed I'm traveling at. I don't notice the noise so much stopped at a traffic light. It happens at low speeds in the city and more pronounce at highway speeds. It doesn't matter whether I'm turning or going straight. It's there all the time.

This may sound strange - but I can say that I feel a "faint vibration" coming from the engine area behind the pedals. And I am NOT even stepping hard on the brakes. My foot is just gently/lightly "hovering" over the gas or brake pedals - and I can feel the vibrations.

I thought it was coming from the new tires I bought 3 years ago which is when I first noticed the noise. Now that I have switch to ANOTHER set of new tires, the problem is still there.

My mechanic could not find anything wrong with the brakes and wheel bearings.

It's a 4Runner 2007 - V6 - 350,000km or 210,000miles.

Any ideas to investigate this further?

Thanks.

mjlmjl

 

[Aquaman1750]

Same issue

I checked all fluid levels to determine if I had low fluids. Everything was good. I called a mobile mechanic whose diagnosis fee was $25. After starting my 2006 SR5 he suspected the hum was the alternator. He told his grandson to get a long screwdriver out of his truck. He held the tip on the alternator and put his ear to the handle and motioned me over and had me listen. You could hear the noise. He changed out the alternator and noise was gone.