EDIT: Important new information added
Thanks to Bishop we now know that Gates pulley # 38008 is not correct for Mazda 3. He confirmed that it is too narrow and will cause belt squeal pretty much right away, which means the belt can be damaged.
The correct Gates pulley # is 36326.
It is also worth mentioning that this pulley is metal.
Just to keep the important info on top, here are the correct pulley numbers:
DAYCO: 89015
GATES: 36326
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OK guys and gals, I have found a very cheap and easy fix for noisy serpentine belt tensioner pulley.
My tensioner pulley started making slight squeaking / squealing noises about 3 years ago (car is 2006), so basically about 1 to 1.5 years after purchase. It was very faint and only during cold morning starts and at certain RPM's. I brought it to the dealer and of course they said it's normal.
I decided to just keep driving and keep an eye on it while the car was under warranty. Since then nothing really happened, I am out of warranty as of last year, but the noise is getting louder and louder and doesn't go away when the car is warmed up anymore.
I know the bearing in the tensioner pulley is shot, I removed it early this year to re-pack the bearing with grease, it was dry and had side to side play, but re-packing it with grease seemed to help a bit and got me up until this point. I knew from the beginning that it was only a band aid fix.
Well, the temps are getting lower and lower and that tensioner pulley was making me feel uneasy, I don't want the pulley to seize when it's -25C outside and take out the belt with it when I'm stuck in traffic. So I started looking for other solution.
First I called the dealer and they only sell the whole tensioner assembly, which is about $140 +tax. Not my coup of tea, since the tensioner itself is perfectly fine. Lucky, when I originally removed the pulley to re-grease it, I measured it. The dimensions are 70mm OD, 17mm ID and 28mm wide, flanged with 6 grooves.
DAYCO # 89015 and GATES 36326. match these dimensions. I went to Dayco website and it turns out that they have tons of part stores across GTA that carry their products. They even have a handy store locator on their website.
Anyway, I called few places in Mississauga and most have the pulley in stock or can easily order one for you. The best part... it's about $27+tax.
The pulley is very easy to change in your driveway and will take about 10-15 minutes.
I changed mine yesterday and with -14C this morning the belt and tensioner pulley were dead quiet.
I will keep you posted how it goes for the next few weeks or months, but I don't expect any problems at all, since the pulley uses exact same bearing as the OEM one.
I took some pics while I was doing the work and if you guys want me to post a short How To or just the pics, let me know, I can do it in few weeks.
Again the numbers are:
DAYCO: 89015
GATES: 36326