Alternator Noise?

I'm trouble shooting a noise that although SOUNDS like a power steering pump, it's coming from the drivers side of the engine bay. It appears as though it's coming from the alternator. The noise increases with RPM and is constantly there. Here are the tests I have done to isolate it at this point.

1. Noise is there but increases its pitch when RPMs increase.
2. Noise is the exact same with AC on or off. Compressor engages fine and blows cold air.
3. Noise is the exact same even when I turn the steering wheel so I'm confident it's not PS.

Do alternators go bad typically? I did some offroading last weekend and I'm wondering if I got some mud in there or something. How difficult is it to get the alternator out? I have 134k miles on the truck.

 

Get you a stethoscope and put it on the alternator with the engine running and listen or a really long screwdriver works too.

 

Both of those sound like death.

 

That's how mechanics have done it for a long time. So..

 

How so? It's easy. Get a cheap mechanics stethoscope from a parts house, I believe harbor freight has them too. Turn the engine on and listen to each pulley in the engine. Don't put the rod on a rotating surface. I've had sounds vibrate throughout the engine and cause misdiagnosis.

 

If it sounds smooth it's good, if it sounds like marbles in a blender mixed with drywall screws or a real high pitched whine you found your part.

 

To answer your questions, yes they do go bad, and I think they are really easy to replace. That being said I haven't done a second gen, but have done a first gen with just an adjustable wrench, a 3rd gen 4 runner (same motor if I'm not mistaken), and a 96 Cummins. Take a look at all of your pulleys and tensioners, and you might as well replace your belt at the same time. If you have a second vehicle, you can take your alternator to an auto zone or Napa and have them test it before you throw down the cash for a new one. Unfortunately I'm not a mechanic, and I didn't stay at a holiday inn express last night, so I don't have the knowledge to trouble shoot a noise unless I'm their staring and listening to the truck

 

My girlfriends alternator pulley tried seizing and it was a god awful screech that would come and go. Just replaced the hole thing, with more time to source a new pulley we coulda done it cheaper

 

Here is the alternator rebuild and clean out thread.

https://www.tacomaworld.com/threads...or-rebuild-mud-cleanout.453757/#post-14645785

 

If the OP can't use a stethoscope I don't think he can rebuild an alternator.

 

Pretty sure I'm capable of using a stethoscope but I've already located the sound so I'm not sure that's necessary. It's plenty loud without an amplification device. Furthermore, I've rebuilt the starter (years ago) so this shouldn't be an issue.

Baller, that's what I need I think.

Thanks for the help guys. I'll report back next week when I dig into it.

 

FWIW the stethoscope from Harbor Freight is $3.99.

I'm having the same issue with my rig and bought one after the dealer said they couldn't pinpoint.

 

I got a digital one from steelman and I love it. I also got the sound isolators as well. Good little tool for locating noises. I also got the old trusty rusty cheap stethoscope as well as a long screwdriver for those pesky fwd cars with pulleys everywhere with no room to fit your hand.

 

Good to know. Might pick one of those up since it's dirt cheap.

 

Giggity

 

My 2015 PreRunner 4.0L is making an oscillating sound when warmed up and idling with gear selector in P and a/c compressor engaged. When the a/c compressor cuts off the oscillating sound stops. When the a/c compressor kicks back on the oscillating sound resumes.
At first I thought it was the a/c compressor - crawled underneath truck with mech. stethoscope. As soon as I got down below I noticed the sound dissipated significantly. Went back up topside and found the oscillating sound to be coming from the alternator.
Truck under warranty - dealer said it was the a/c compressor - It was not. Still making the oscillating sound. Toyota ate a $556.00 bill for a botched diagnosis.
Dealer Fixed Operations Director claims he's going to bring in a Toyota field Technical Specialist to resolve - will take 1 to 2 wks. for this to happen. This person covers dealerships all over the state.
I still contend it's the alternator. In a day or 2 I'll take the truck to a place that's been rebuilding alternators and starters for me for the last 30 yrs. His opinion may mean nothing to the dealer, but it will make me feel better to know if it really is or is not the alternator.

 

Just some closure for you guys....finally got back from vacation and had time to get under the truck. Over the last week I remembered I'd gone through a few idler pulleys about 100k ago after some deep water crossings. So I decided to check that out. I suspected it was the lowest pulley (for obvious reasons) but I was wrong. turned out to be the top most #2 idler pulley was totally shot. It wobbled a bit on its axis and the bearings were completely toast. Sounds like a can of marbles. Replaced it and we're good as new. Did the belt while I was in there too.

 

Yeah, but they are junk like other HF stuff.

I got mine from HF in 1996 as a "free gift" for ordering $25 of stuff. Just last spring the rubber tubing cracked and I had to go to Ace Hardware and spend $1.28 to get some replacement tubing...

 

Could be.

I bought mine because $3.99 and because unlike a lot of HF tools, it had great ratings.

Good enough for me to use a half dozen times. Only issue I had with it was the extension was hard to thread on, kept wanting to go crossthreaded. All good now.