Hey, thought I'd post a solution I found to something that has been plaguing me for quite some time.
This is on my own 2008 Odyssey Touring, J35A7 VCM engine with hydraulic serpentine belt tensioner. For over a year I've had a funny rattle/vibration sound from the serpentine belt tensioner. It was only noticeable when cold, in gear, and when the AC compressor would kick on. In Park it wasn't as noticeable. I could go under the hood and put a long screwdriver on the tensioner bolt and feel the vibration. I don't recall exactly when it first happened but I remember the first thing I did was replace the tensioner as it had around 180K or something at that time so figured it was worn out and time for a new one. I was shocked when a new genuine Honda tensioner it didn't fix it. Since it only happened with the AC on I then figured it must be some extra vibration caused by an aging AC compressor and I wasn't going to bother with it. However, at around 203K the AC quit working.
I found a leak in the condenser and decided that with such high mileage it was time to rebuild the AC system. I replaced the AC compressor, condenser, and both expansion valves. When that was all done, the AC worked great (and still does) but that same vibration and rattle sound was still there when cold. While a visual inspection of the harnonic balancer showed no issues I decided to replace the harmonic balancer anyway since I was placing an order from Bernardi for some other parts. They are prone to failure on these engines and with the 218K that is currently on it thought maybe it wasn't lined up or somehow was causing the issue. I installed that last week. Nope. Didn't fix it.
After scouring the Internet and finding nothing at all about vibrations/rattles on the belt drive attributed to anything other than a bad tensioner I decided the only thing left was the belt itself. I'd replaced it at timing belt time at around 180K with a Bando belt but it had been making that noise prior. I don't recall what belt was on it before--probably a Dayco from Advance Auto. I've since learned Dayco belts aren't very good so I went with the Bando that time. I've installed many of them over the last couple of years and never had any issues or come backs with them. However, being at my wits end with this I decided to run to the local Honda dealer and buy a genuine Honda belt (supposedly made by Mitsuboshi.) When I brought it home and compared it to my Bando belt that still looked fairly new I was shocked. I've never compared two new (or lightly worn) belts before. I've compared a new Bando with a worn OEM and never noticed too much issue. However, below is what I found.
The Bando belt isn't that old and still has lots of life in it as is apparent by the the labeling still looking fresh. My special tool for measuring the grooves (not shown) showed it to be in great shape with very little wear on the groove side. Using a caliper I measured the thickness of both belts:
Bando: 4.38mm
![153589]( "153589")
Honda belt: 5.09mm
![153590]( "153590")
As shown above, the Bando belt is nearly 0.7mm thinner than the OEM Honda belt. That's nearly 20% thinner than the OEM belt. When you hold both at the same time there is a huge difference in the feel of the belts. The Honda belt is thick and rigid while the Bando belt felt thin and wimpy.
I installed the Honda belt and started it up. No more vibrations! I thought, well, I need to do a cold start so I waited until this morning and started it up again. Noise is gone.
Lesson learned: I've heard good things about Bando belts and have never had any issue with them. Their <$10 cost on RockAuto and Amazon makes them a good option when compared to the $53 price tag (discounted from the $64 the parts guy wanted at first) that Honda charges. However, the results speak for themselves. I bought the Bando belt on Amazon so maybe there are fake Bando belts too. All I know is a cheap belt fit nicely and never squealed but caused me much headache.
As to why the thinner belt caused the tensioner to vibrate, I'm not sure. All I can think of is it tends to slap around a bit more than the thicker, heavier belt. It does go directly from the AC compressor to the tensioner so maybe there is a weird vibration there that causes the belt to slap a bit and vibrate the tensioner. For now I'm not able to duplicate the vibration and rattle anymore when cold so I'm happy. Just thought I'd share with everyone else since I've found nothing about anything like this anywhere on the Internet.
This is on my own 2008 Odyssey Touring, J35A7 VCM engine with hydraulic serpentine belt tensioner. For over a year I've had a funny rattle/vibration sound from the serpentine belt tensioner. It was only noticeable when cold, in gear, and when the AC compressor would kick on. In Park it wasn't as noticeable. I could go under the hood and put a long screwdriver on the tensioner bolt and feel the vibration. I don't recall exactly when it first happened but I remember the first thing I did was replace the tensioner as it had around 180K or something at that time so figured it was worn out and time for a new one. I was shocked when a new genuine Honda tensioner it didn't fix it. Since it only happened with the AC on I then figured it must be some extra vibration caused by an aging AC compressor and I wasn't going to bother with it. However, at around 203K the AC quit working.
I found a leak in the condenser and decided that with such high mileage it was time to rebuild the AC system. I replaced the AC compressor, condenser, and both expansion valves. When that was all done, the AC worked great (and still does) but that same vibration and rattle sound was still there when cold. While a visual inspection of the harnonic balancer showed no issues I decided to replace the harmonic balancer anyway since I was placing an order from Bernardi for some other parts. They are prone to failure on these engines and with the 218K that is currently on it thought maybe it wasn't lined up or somehow was causing the issue. I installed that last week. Nope. Didn't fix it.
After scouring the Internet and finding nothing at all about vibrations/rattles on the belt drive attributed to anything other than a bad tensioner I decided the only thing left was the belt itself. I'd replaced it at timing belt time at around 180K with a Bando belt but it had been making that noise prior. I don't recall what belt was on it before--probably a Dayco from Advance Auto. I've since learned Dayco belts aren't very good so I went with the Bando that time. I've installed many of them over the last couple of years and never had any issues or come backs with them. However, being at my wits end with this I decided to run to the local Honda dealer and buy a genuine Honda belt (supposedly made by Mitsuboshi.) When I brought it home and compared it to my Bando belt that still looked fairly new I was shocked. I've never compared two new (or lightly worn) belts before. I've compared a new Bando with a worn OEM and never noticed too much issue. However, below is what I found.
The Bando belt isn't that old and still has lots of life in it as is apparent by the the labeling still looking fresh. My special tool for measuring the grooves (not shown) showed it to be in great shape with very little wear on the groove side. Using a caliper I measured the thickness of both belts:
Bando: 4.38mm
Honda belt: 5.09mm
As shown above, the Bando belt is nearly 0.7mm thinner than the OEM Honda belt. That's nearly 20% thinner than the OEM belt. When you hold both at the same time there is a huge difference in the feel of the belts. The Honda belt is thick and rigid while the Bando belt felt thin and wimpy.
I installed the Honda belt and started it up. No more vibrations! I thought, well, I need to do a cold start so I waited until this morning and started it up again. Noise is gone.
Lesson learned: I've heard good things about Bando belts and have never had any issue with them. Their <$10 cost on RockAuto and Amazon makes them a good option when compared to the $53 price tag (discounted from the $64 the parts guy wanted at first) that Honda charges. However, the results speak for themselves. I bought the Bando belt on Amazon so maybe there are fake Bando belts too. All I know is a cheap belt fit nicely and never squealed but caused me much headache.
As to why the thinner belt caused the tensioner to vibrate, I'm not sure. All I can think of is it tends to slap around a bit more than the thicker, heavier belt. It does go directly from the AC compressor to the tensioner so maybe there is a weird vibration there that causes the belt to slap a bit and vibrate the tensioner. For now I'm not able to duplicate the vibration and rattle anymore when cold so I'm happy. Just thought I'd share with everyone else since I've found nothing about anything like this anywhere on the Internet.
