[John Clark]

Do you have an LX, EX, EX-L, or Touring? The EX-L and Touring use a tensioner with a hydraulic piston for keeping tension. The LX and EX use a mechanical spring inside the tensioner. If the belt is routed properly then you should check the tensioner itself and make sure all the bolts are in the tensioner assembly. If it's the mechanical tensioner then there is a small bolt on the bottom of it that helps hold it in place. If it's the hydraulic style then you need to make sure the bolt is in the hydraulic cylinder and the hydraulic cylinder is good.

 

[John Clark]

I would check your installation of the tensioner. Also, I'd check to make sure you have the proper belt.

 

[John Clark]

I really like jnissen's reply. Just use OEM parts. However, I'd like to offer a couple of conceptual insights as to what MIGHT be happening. It could be great to use an app on a phone or iPad (SPLnFFT) that can show pictures of sound frequencies and levels before and after the repair. The belt/pulley system is quite complex dynamically, with the belt sections acting as springs and the effective masses of the pulleys and tensioner acting as masses. The tensioner is a Mass-Spring-Damper (MSD) system on its own. In addition, the teeth of the belt on the pulleys deflect, modifying the effective spring. The resonant frequency of a system is approximately f(hz) = 2pi*sqrt(AE/L/M). A is the cross sectional area of the belt. E is Young's modulus "stiffness of the belt", L is belt equivalent length, and M is the "effective mass" of the pulleys & loads referred to the belt. So... at a first level, the area of the after market belt is lower. The belt is softer so E is lower. These tend to drop the natural frequency of the belt. However, the square root in the above equation tends to reduce these effects and is probably not enough by itself to make your noise. The tensioner has its own natural frequency. So if the natural frequency of the tensioner connected with the belt is close to the lower frequency of the belt and pulleys you can get an audible beat frequency that is the difference between the two frequencies. This is the effect of two people whisling high notes that are just a bit different from each other. You hear the difference between them. You mentioned a "rattling" sound". That can also be bearings that are shot in the pulleys (did you check the bearings in the pulleys?). You mentioned: "weird vibration there that causes the belt to slap a bit and vibrate the tensioner". They can make rattling sounds by again interacting with the belt. In this case the resonant frequencies could be higher since the pulleys and belt are creating their own resonance with lower effective masses involved. Belt slapping is yet another dynamic similar to vibrations in the string in a musical instrument - resonances love to absorb energy at their natural frequency. I hope no one tries to go down the theoretical path, as you may never return. Let the Honda engineers agonize over this... So.... I'm glad you found that replacing with OEM parts and with a new tensioner worked out.

Just saw this.

The entire tensioner assembly was new right from Honda and included both pulleys. When the rattling started it was the first thing I repalced because I could put my long screwdriver on it and feel it shaking. Imagine my dismay that after $160 for the new Honda tensioner I still had the vibration/rattle. It did tend to happen more with the AC compressor running so I thought it might be a vibration in the compressor causing it. Later, after replacing my entire AC system, including the compressor that rattle was still there. I even replaced the harmonic balancer. It was 100% the thinner belt. While it doesn't squeal and lasts a long time it allows something to vibrate that tensioner. It may only happen with the hydraulic style tensioner as I haven't noticed it with the mechanical internal spring type tensioner.

I'd like to experiment and try some other brand belts to check their thickness. Buying a $60 belt is not what I really want to do, even for others cars, but obviously will if I have to. I took the recommendation on Bando from Eric O at South Main Auto. I've never had an issue with the Bando belts on any other vehicle, though.

 

[John Clark]

John, just curious, about how many Odysseys you have used these Bando belts on? How many were EX-L and Touring having the hydraulic tensioners?

Also, how urgent of a problem do you think it is to address? Think it will cause other things to fail?

Like I mentioned above I may have the same issue with my '07 Touring which has a Bando belt that was installed about 8 months ago. Based on what you have written it seems that unless there is an obvious problem with the tensioner that it is less expensive to try and replace the belt first.

Thanks, I appreciate the advice.

That I'm not sure of. I've used quite a few and on lots of different vehicles. There is nothing wrong the Bando belt itself. I still think they're good belts. They just seem to rattle the hydraulic tensioner when cold and in gear and moreso when the compressor is engaged. When warmed up it doesn't seem to be a problem. I suppose it could stress the mounting bolt which does have a tendency to break on some vans. I've not experienced a bolt breaking on mine but have seen it on one van I worked on (it happened prior to me working on it) and have seen it reported here.

 

[John Clark]

I would like to add my story on this thread as it solved the exact problem on my 2010 Odyssey. I'm a ASE mechanic and have no problem saying I needed help solving this problem.

My issue started in December 2018, after I finished a complete timing job to include Aisin timing component kit, Honda side engine mount, NGK plugs and a BANDO sepentine belt. Engine ran nice and smooth, no codes etc afterwards but I did recognize a rattle noise of sorts when the vehicle was placed in gear. I double checked all installed mechanicals, focused on the plastic shields that I had removed, going as far as removing 1 at a time and driving for a period of days to try to isolate noise. Months go by and every morning when my wife starts the car and backs out of garage the rattle noise just drove me bananas.

Finally, a few weeks ago, I reached out to this forum for help. Opinions generally focused around the timing belt tensioner causing the rattle. This perplexed me as this was a part time rattle with specific conditions, when the car was cold, in gear and at idle rpm. I reasoned a faulty hydraulic tensioner would present whether the car was in park or in gear. A gentleman named BertS was the first to chime in with a alternative, referring me to this discussion and asking if I installed a Bando serpentine belt. I looked through my parts receipts, and sure enough a Bando belt. I read through this discussion and everything John Clark described fit my situation. I decided that even though this noise did not present as a serpentine belt issue, I was going to remove the Bando belt and reinstall the old Honda belt that I removed in 2018 since I had kept it and it wouldnt cost me anything. Wasn't too hopeful. I removed the 14000 mile Bando belt and compared the thickness to the 40000 mile Honda belt as John did. Sure enough, the Bando belt measured .018" thinner than the Honda belt.

I installed the old Honda belt and the noise completely disappeared. Its been over a week since and engine completely silent. Morals of the story: 1.Your never too old to learn new things 2. Ask for help if you need it. 3. Honda 3.5 engine needs Honda serpentine belt.

Thanks for the post. I'm surprised you made it here. Most professional mechanics shun Internet forums, because on the forums many people often lack experience and post on things they know nothing about. It's nice to have some info from professional mechanics who do this every day. Second, you guys often get your info from Identifix and other professional forums/databases. I'd be curious to know if there is anything regarding this issue on any of those sites. I only wish I had access to those sites but they are limited to professional shop people only. I am semi-professional where I do work for others on my days off from my regular job but have no ASE's or affiliation with a professional shop that would allow me access to those sites and info.

When you share knowledge, you gain knowledge. That's just how it works. One of the pros I watch on YouTube states that on many of his videos. Many professional mechanics forget this and don't ever want to jump on a forum like this. There are things to be learned by all of us and we all benefit when sharing the knowledge.

Thanks again!

 

[John Clark]

It was a lower pitched rattle sound. I could take a long screwdriver and put it on the bolt while the engine was running and feel it at the tensioner.

It is also common to have some of the heat shields rattle underneath the car so that should also be checked.

 

[John Clark]

Sometimes it seems like it's related to the engine being cold when it's really just related to the RPM of a cold engine. This is what I found with the serpentine belt tensioner rattle. It only happened when cold, with the AC on, and in Reverse or Drive at idle. When it warmed up it went away. However, when I got more into it, I found I could make it happen any time if I was able to put it in gear and get the RPM just right at 11-1200 RPM, the same as where it idles when cold.

 

[John Clark]

It does sound similar. Try removing the serpentine belt and see if the noise goes away.

 

[John Clark]

Did you remove the belt first and run it to see if the noise was still present, as I suggested?

 

[John Clark]

It's an important step (at no cost) to determining the location of the noise.

 

[John Clark]

Also, to note, the hydraulic tensioners require a somewhat special procedure for releasing tension. You are only supposed to apply steady pressure and allow the hydraulic piston to move slowly. If you force it hard, as you would with a spring, with a lot of leverage, you can damage the hydraulic piston assembly.

 

[John Clark]

I'm still here. Glad to have helped!