Humming Noise from engine driving me crazy

[mchancellor]

Hello all, new here but have a question about a noise to see if it's common or serious.

My 2005 Runner started making a quiet humming/buzzing/moaning from the engine bay yesterday. It only comes about after a short trip/few miles and it's only when it idles or is stopped/just starting off from stopping. It happens in drive or park. There are no vibrations and it almost sounds similar to a bad pump or belt when i listen with the hood up. Not very loud at all but loud enough to drive me insane.

Maybe the alternator?

Thanks for any help!!

 

[KingPrat]

AC or defroster on? Could be the pump cycling and a bad pulley bearing?

 

[mchancellor]

AC is on, I will turn it off next trip- leave it off and see what happens. Thanks for the quick reply.

 

[CookieRoe]

I thought I saw a thread somewhere that explains a humming coming from the engine (you can hear it when you wash your truck and leave the key on ACC to hear the radio). If memory serves, it's the breaks cycling to give constant pressure to them. I could be wrong.............

 

[mchancellor]

if the key is in ACC, the noise is not present only when it is running. The noise gets just a tad louder with the change in idle speed (goes up) and quieter when it drops back down, however not once i accelerate (maybe its just so quiet I can't here it at that point.)

 

[me_rikey]

i'm going to go on a limb here and ask if you've checked, and/ or cleaned the idle air control valve?

 

[NJshadow93]

Are you sure it's coming from the engine bay? If you can get a video and post it, that's the best way to get help on here. It's so difficult to diagnose noises without hearing them.

 

[mchancellor]

It was indeed the alternator- or at least I'm assuming so, drove it to a friends house last night the noise was worse than ever and this morning it wouldn't start, and remote unlock would not work. The battery indicator says its fine? But I don't know how that's possible...I guess I will start with replacing the pair and hope for the best. Thanks for the help guys

 

[BlackWorksInc]

If you or your friend have a DMM (Digital Multi-Meter) or just a regulator Voltmeter, perform the following checks.

~From Battery Post to Battery post before running the engine (or if you just ran the engine, run the high beams for 30 secs, turn them off and check voltage), A good battery should be between 12.6~12.9v

~Now check the voltage between your terminals and clamps (positive post to postive clamp, negative to negative clamp) Your voltage should be 0~.05 (50 milivolts), this is a test for voltage drop, which can be caused by a number of conditions.

~Now with the engine idling, check battery voltage post to post, you should have somewhere between 13.6~14v, but no higher than 15v, this will indicate the function of the Alternator. If you really want an accurate voltage reading go to the positive post on the Alternator, and then a body ground. (the reasoning for this is that when the vehicle is turned on the Alternator becomes the most Positive portion of the circuit, you can also check the voltage drop between the alternator to the battery post by going from the Alternator post to the battery post, you should see no more than about half a volt drop on this cable.

 

[niko303]

I’m grave digging here but I have the same issue. A whine when in park or neutral, it goes away when I’m driving. I have noticed a slight struggle when turning the car on recently. Thanks for the heads up on using the volt meter

 

[benztech82]

I’m grave digging here but I have the same issue. A whine when in park or neutral, it goes away when I’m driving. I have noticed a slight struggle when turning the car on recently. Thanks for the heads up on using the volt meter

Buzzing noise from the engine that changes with rpm is a common thing for v6 engines its an idler pulley beside ac compressor. It takes 10 minutes to replace it just loosen tension of the belt and at the same time replace that pulley. I just did most mine too.

Sent from my Redmi 4 Prime using Tapatalk

 

[RAD4Runner]

Could also be the power steering pump? My first-gen's has a low pitch whine / high-pitched hum. Noticeable but tolerable.

...It takes 10 minutes to replace it just loosen tension of the belt and at the same time replace that pulley. I just did most mine too.

Nice! Must be similar to the Corolla; My daughter and I replaced it quickly, too. We spent more time ordering and buying parts than the actual job itself

 

[MtbRida444]

Exact noise popped up for me last night

Just for insight I just did a job on my 97 4runner 2wd 6 cylinder which was rooted in a misfire I kept getting over the years which was in cylinder 3. Rebuilt and reinstalled all fuel injectors. Got rid of the misfire. Now about a week later this noise i have not recognized or heard from my car pops up and have no idea what it is. Coming from drivers side upper/mid engine. Any luck on finding out what it is? Hear it mostly when idle/ end of decelerating.

 

[mynamesrickgrimes]

2nd on power steering pump - had that same sort of noise on my V6.

 

[holmtech]

Sounds like the alternator for sure. When one of the 4 diodes fails it stops charging well and makes that noise. Your days are numbered at that point until your battery dies from powering everything and not getting much charge. A good confirmation is to check the voltage while the engine is running. If it isn't 13.5 volts or better then alternator failure is confirmed.

Be sure to check your battery, because this has put a strain on it. If it's 4 or more years old, it's a good idea to just replace the battery along with the alternator if you can afford it. Plus serpentine belt, and maybe tensioner.