Could it just be the belt squeaking when the alternator has a large charging demand on it? One way to check this is to put a large demand on the cars electrical system- bright lights on, A/C on full blast if the squeak begins happening have a container of water handy, a garden waterer is perfect and pour water on the alternator belt. If it stops squeaking it is a loose belt.
These belts take a lot of tension to tighten and run noise free.

These belts are also driving the a/c compressor

This doesn't seem like the most professional method does it. I have seen experienced dealer technicians using this method to quickly diagnose a belt that needs to be tightened. These belts can seem very tight but will begin to slip when a high demand for electricity is put on the alternator.

Alternator bearings are of course another suspect but Toyota components like alternators, starters and water pumps are well made. I have driven Toyotas exclusively since 1985 and have never replaced any of these components on them. Maybe I am just lucky. When I drove Chevys and Fords before 1985 I would have to rebuild starters, alternators and replace water pumps almost as routine maintenance. Hopefully they have improved their reliability.

 

I would also look at the power steering pump. Look under the van and see if it's leaking. Our PS pump has started making noise but it's not constant like you describe. You can go nuts trying to isolate a noise. We had a Corolla that made a squeak at speed. Turned out to be the hood barely in contact with the fender making a high frequency squeak.

 

Interesting point on the PS pump. The PS pump on our van has always had a little drop of fluid hanging on it. It is a very very minor leak. It does not drip, or at least i cannot see a drip.

I wipe it every oil change, for the last 75k miles and it never gets worse. I've always wondered if it's the pump leaking or one of the hoses is not fully torqued. Never worried me too much.

I would go under the car later and listen to the PS pump with the mechanic's stethoscope.



The question is, if it is the PS pump, why the squeak increases slightly as the electrical load increases?



Also, since it's relatively cheap and easy to replace, i may get a new high quality belt as well and just replace the belt i have now. It's only a year old, but it is a more generic brand and i know some belts do get noisy after awhile.

 

I have an 07 Toyota Sienna XLE with 173,000 miles. I kept getting a pulley noise in the serpentine belt area since I bought the van 2 years ago. I replaced both serpentine belt idler pulleys and the tensioner pulley. They were definitely worn but I still had a noise coming from the serpentine belt area. Next I changed the serpentine belt suspecting that might be the problem. The old belt still looked perfectly fine and replacing the belt didn't fix the noise. During this whole Fiasco of trying to diagnose the problem you could feel an engine vibration that was slowly getting worse and a slight knocking noise. One day the noise got loud enough that we narrowed it down to the rear bearing on the alternator using a mechanic's stethoscope. It sounded like a loud knocking noise and you could feel a strong vibration on the engine. Replaced the alternator and the sound was FINALLY gone!

 

FYI there's also a clutch pulley on the end of the alternator that can go bad and cause noise and vibration as well. I figured that might have been the problem with mine but didn't want to go through that headache of replacing just the pulley and it turn out to be the whole alternator. So I just replaced the alternator and it came with a new pulley on it.

 

The brown rust deposits you noticed around the pulley are most likely dried-up grease leaking from the alternator bearings where the squeak is coming from, increasing with load and speed. The alternator bearings are sealed with a high temperature polyurea grease from the factory. But at 155,000 miles, it may be time to replace the alternator. I had to do that on my 2004 Sienna XLE.

 

I just replaced the alternator on my 2007 Sienna XLE that also just turned over 150,000 miles. I had no problems but did so as a matter of preventive maintenance. I will be making a 4200 Mi. round trip to Ohio from Arizona in July and rationalized that a cost of $170 + $60 core charge was far cheaper than the inconvenience and danger of getting stuck hundreds of miles from assistance in 100+ degree weather. I might have done that when in my 20's but not now. This likely doesn't help you in your indecision but I don't think the car will run very long once the alternator fails. I probably would have procrastinated if only driving locally since I had no symptoms. In your case I'd probably replace. As information, I purchased a Denso (OEM) re-manufactured alternator from Summit Racing in Ohio so that I could get my core charge back when I arrive. Denso has a plant in Los Angeles which drop shipped the alternator to my location and within 4 days free of shipping. Good luck.

 

My alternator failed this week. We have a 2001 Sienna XL with 239,000 miles. We had no indication that it was going bad. Stopped at the store and when we came out and started again the alternator light was on. Checked it out and found it had no output what so ever. Replaced it with a OEM rebuilt and all is fine. I feel 239K is good service.

 

From your description, it sounds like a bearing in the Alternator is bad. As to the life of alternators, that varies from vehicle to vehicle and depends on many different things. If a battery has shorted plates in it, that can cause failure. If you attempt to jump start another vehicle and get the cables reversed or the other vehicle has problems with it's charging system then the alternator can be damaged. However, your problem sounds more like either normal wear and tear or the alternator belt was adjusted too tight. Over tension belts are responsible for a large number of bearing failures in alternators. As to my personal experience with the Seinna alternator, we own a 2006 Sienna Limited with around 240,000 miles on it and the alternator is the original and seems to be functioning as well as when it was new.

Hopefully this is helpful.

Randy

 

yeah...don;t think its alternator....I would check for cheap easy solution before alternator job...get a spray can of belt dressing and spray on the belt while running to see if noise stops.... if it does...then you know problem.... then try either tightening or loosening belts to remedy.... If it still makes noise...then would be bearings or something els...

 

If it was me, I would replace with a high quality belt, like Continental (Formerly Goodyear Gatorback). While the old best was off, spin each of the pulleys by hand and see if you can recreate the squeak.

 

I will swap the belt first. I just got a brand new Gatorback.





For those of you who have replaced the alternator, are there any useful tips/tricks you can share?
My own research shows that the alternator is not very easy to pull out from the 3.5L Sienna. It can be a painful job, unless i remove some the radiator/fan components and hoses.

 

Spritz a bit of water on the belt while it's squeaking. If it immediately goes away, it's most likely the belt.


ChrisFix did a great video about this subject. It's worth watching:


https://youtu.be/AEUe6uKxTv8

 

danmm7 - Any update on your noise? Did you replace the alternator?

I've been chasing a belt noise for a few weeks now, I've replaced the tensioner, two idler pulleys, water pump, belt, and power steering pump and still there is a belt squeal/chirp that I can't pinpoint. Next up to replace is the alternator.

I've tried listening to the pulleys and couldn't tell the difference. Sprayed water on them and the noise is still there. I have a 2007 with 156k miles.

 

I hate when members don't post their fixes. Posting back solutions make the forum work!