I've got a noise coming from something operating on the drive belt but have been unable to pinpoint it. Could use any/all help.

Details:

• 2005 lx I4 approx 121k miles
• Belt replaced at about 110k miles, noise started around 119.5k miles
• Noise is an intermittent rythmic whine or growl. not as high pitched as a typical worn bearing
• Idler pulley replaced at 120k, no effect

I'm confident it's something on the drive belt. If the car is making the noise, and I shut down and take the belt off and start it, the noise is gone. Even thoughthe noise is intermittent, I've done this a few times and am confident it's something along the driveline.

The noise does not seem to be effected by outside temp. Meaning, it can be there when it's cold on starting one morning, or warm, and then not th enext. I would say it's there 70% of the time. Occaisionally, if I blip the throttle a few times and rev the engine in neutral, it will go away, but this only works sometimes.

I verified it's not the belt itself. I had replaced the oem belt due to mileage, but it wasn't showing any cracking or glazing, so I kept it as a spare. Ive swapped the OEM back on since the noise started, and it made no difference. Noise was still there, and was still intermittent.

Alternator output checks out fine. The noise is seemingly uneffected by turning the wheel lock to lock. If it was PS pump I thought it might change in doing this, but it doesn't. It is also not effected by AC compressor kicking on or off.

With the belt off, all the pulleys turn smooth. Noneof the pulleys seem to have excessive play. The AC pulley and the water pump pulley have a vey small amount of play I can feel if I grab the pulley and move side to side, but it's not much...barely noticeable. There is a very slight squeek from the water pump pulley if I turn by hand. It turns smooth and free with no binding however.

I don't have a stethescope, but using a long metal probe to each pulley, I really can't pinpoint it. My coolant is right at the min level in the reservoir. I can't imagine that would matter, but I'll be topping it off anyway. I remember noticing that a few thousand miles ago and noting I needed to top it off, so the level has remained constant.

Any ideas? Any tests/checks I can do before giving up and bringing it in?

This is my daily driver, so I'm driving it like this 70 miles a day for the time being. Haven't noticed it getting any worse.

 

I once had a Suburban w/ serpentine belt that made an intermittent growling noise. It turned out to be the auto-tensioner bottoming out, due to slighlty loose belt or faulty auto-tensioner. I replaced both and fixed the problem. It was hard to duplicate, but I finally saw it happening one day.

Check your auto-tensioner for a change in pointer position from before starting to running. If postion changes replace the auto tensioner. The tensioner pulley also has a bearing that can fail and spring can become weak. Shop manual has some good guidance on testing and repair.

If you don't have a shop manual and want to DIY, check ebay seller automanualsource for an emanual for $21.99.

good luck

 

I will definitely look at that.

I actually put a wrench on the tensioner today and put a little force on it each way then started it to see if it changed anything. It didn't, but the reason I did this is because when I put the belt on today I thought I noticed the tensioner kind of "settling" a little after i had released it.

My mom has one of the same generation so my dad probably has the manual. Admittedly, I never gave much thought to the tensioner itself being the culprit. I do remember when I bought the pulley, the tensioner was only like 70 bucks, but I opted to be cheap and just got the pulley.

Thanks!

 

After testing the tensioner, I ruled that out. Narrowed the noose down to either the water pump or the alternator. I changed both, but it ended up being the alternator.

I put in a remanufactured alternator, but picked one with a low core charge and just opted to keep my old one as a spare. The remanned one I got has a lifetime warranty, but it's a cheapie from a chain store. I can swap it out in 10 min with one 14mm wrench so I am keeping the old one in the trunk with a wrench for noe just in case. Eventually I will rebuild it as I have more faith in it being rebuilt than the replacement.

Figured I wouldnpost since so
Many threads end without ever knowing the outcome

 

And we all appreciate knowing how it turned out.