Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Weird sound from the pulleys

I have a rattling sound coming from the pulley side of the engine. I am pretty sure, it is not coming from inside the engine itself. Many mechanics tried to pinpoint the sound with the stethoscopes, but unable to locate where the sound is coming from. I do not want to spend money on replacing every suspected part.

Little background: This noise started after the engine bay got flooded (but no damage to the engine).
2005 Toyota Corolla S, manual transmission.

Link to a video of the noise from the car

Anyone experienced in these type of issues care to comment?

Thank you.

Sounds to me like the hydraulic belt tentioner is on its way out. It happened on my Corolla also.

If you don’t want to spend any money on parts just drive it until a pulley falls off and then you’ll know what part you need. Sounds like water corroded the bearings in the belt tensioner. Also make sure your water pump does not have a small leak.

I can’t hear the noise, sorry. My inadequate PC won’t do that.

I don’t know a Toyota Corolla from a tan Crayola (They’re not sold near me.), but I can read and I have a couple of questions…

The flooding could be a red herring.

When does it make noise? All the time? How about while accelerating from a stop up to 30 mph?

Do you or does anybody know if this car has a 1ZZ–FE (Toyota’s designation) engine?

Has anybody checked the right-hand engine mount?

Toyota issued a 2 page TSB (Technical Service Bulletin) # EG027-06 (April/06) for their technicians to use in diagnosing noise from the mount and they had to manufacture a revised mount.

This bulletin applied to some 2005-2006 Corolla and Matrix vehicles with the 1ZZ–FE engine.

It is pretty hard to diagnose a noise over the internet that at least 2 mechanics can’t pinpoint with a stethescope but if it was my car, I would try this: Remove the serpentine belt. start and run the car briefly. See if the noise is there with the belt off, If the noise is there, then it is caused by nothing driven by the belt. Look elswere. If the noise stops with the belt off, turn every pulley by habd looking for any roughness or play.


A faulty belt tensioner or alternator bearing are the most likely culprits, water pump, power steering pump after that, but it’s only a guess. Does the noise change when you increase demand for electricity from the alternator, like switching the headlights from “off” to “full bright”? That might provide a clue. Likewise listen for noise changes when turning the steering wheel, or turning the heater on and off.

The sound exists all the time when engine is running. It increases with rpm. No change in noise as I turn on ac/ heater. My headlights are always on. Maybe that is why I haven’t noticed any difference when headlights are on. Anything else can turn on to put load on the alternator?

The common consensus among mechanics that I showed it to is that the noise might be from the idler pulley, but no one is sure. I have to replace some part at some point. I’ll try replacing the belt tensioner and belt. Will report back with results.
Thanks for all your input. Much appreciate it.

Did you not see the reply by oldtimer? Remove belt and run car for a couple of minutes like he said to see if noise is still there.

There’s usually a way to turn the headlights off completely, check the owner’s manual. How would a burglar drive through a neighborhood late at night undetected in their Corolla without being able to turn off the headlights? … lol … If turning the headlights off is just not possible on your Corolla, then you could switch the headlights between bright and dim. That would vary the alternator load. If you have a rear window defroster, those tend to draw a lot of current too.

Sorry, for the late update.
I got the belt and tensioner replaced with a Gates brand belt and tensioner from Rock Auto. It solved my problem completely. I forgot the time when my car was this quiet. Many people had warned me that my pulleys are going to come off if I don’t replace them. I already pushed my luck with this issue for over 2 years. Lately, I have plenty of bad luck, so I didn’t want to take any more chances.

Even though I think the sound was coming from the Idler pulley, I decided to take the advice of some of you guys and replace the tensioner too. At some point, I need to take care of it too. Thank you all for your input. You guys rock!!