1996 2wd 4runner with 183k. This sound comes and goes but lately it's been happening every day. Timing belt was replaced around 136k. I've included a video. The sound appears the last 25secs. It's a whining noise that gets louder when RPM's increase. I just want to make sure I'm not going to destroy anything while driving. Plus I'd like to fix it. Thanks in advance.

http://www.flickr.com/photos/51001863@N02/4686288995/

 

sounds like a prime suspect of the ac tensioner pulley.. either it needs tightening or the bearing on the pulley itself is bad. Replacing the part is cheap and literally takes 15 min to do. I would take it to a auto shop and have them put a auto stethoscope to all your pulleys just to make sure and if you're nice I bet they'll look at it for free

 

so is it something I can easily replace myself? If it's that easy and cheap I wouldn't mind replacing it just for grins. If it is a bearing, could it possibly seize up while driving? or just get louder?

 

I'll do that too! Mine sounds like that and now when i turn my A/C on it the belt squeaks probably due to its not tight enough and the other noise probably the tensioner pulley.

 

Well -- took it to the shop and they said it's the alternator and a/c tensioner pulley, just like JWaldz said. I went ahead and replaced the alternator but didn't notice a difference I probably should've tried the pulley first....Anyway I had to order the pulley from dealership and should be here tomorrow. Hopefully I can replace it tomorrow evening. If that doesn't fix it I have a mechanic friend (lives 3hrs away ...otherwise he'd fix it) who thinks it could be the water pump. Hopefully not. stay tuned...

 

My ac tensioner has about 2 inches of play in it. You should've tried wiggling it first.

 

mine made the same sound when it went out.... I have an extra laying around i can sell you

 

replaced a/c tensioner pulley and no more noise!! whoo hoo! JWaldz was right on the money. Should've tried that first before taking it to the shop. Not sure if shop was trying to jip me or not but replacing the alternator did nothing. Luckily I did that my self and spent less than half of what they wanted to do it. Note to self: try the cheapest repair first. Thanks guys for the help. Yotatech never fails!

Yukon -- thanks for the offer but luckily dealership got one in within a day. Probably would've tried if first if O'reilly's could've figured out which pulley I needed....

 

I see this all the time described as the a/c tensioner pulley. I can't find that in the FSM. Is it "officially" called the idle pulley?

 

yeh the Chilton and Haynes manual call it the idler pulley as well. The repair shop that diagnosed it called it a/c tensioner pulley though. Maybe that's why O'reilly couldn't find it. Should have told them idler pulley. But I did notice that there are also idler pulley's shown with the timing belt so maybe call it a/c idler pulley??

 

The technical name for it is the idler pulley.. the common nickname for it is the a/c tensioner pulley or a/c idler pulley. I bought mine at Advanced for a few bucks and a lifetime warranty. It took forever to find the part bc we weren't looking for just an idler pulley. It actually took me to take a picture of the part with my cell phone and opening the box of the ider pulley to see that it was the same item. If you ever have any issues with it again, like the kball's picture shows in the 2nd pic, try adjusting it first. That bolt loves to come loose and causes a light whining noise from play in the line. The long term effect of it being loose without knowing causes the bearing to go out on the pulley resulting in the full time whine you were having. Glad you got it all taken care of.