I know this will be a bit vague going in, but I'd appreciate any help anyone might be able to give...

Midway through DBR06 I started to notice a rattle emanating from under the car, whenever I was at ilde RPM. At the time, I dismissed it as a noisy clutch (I have a SPEC Stage 2+ that has sounded like crap ever since first installed, 6000+ miles ago).

Well I just put the car up in the air and started it, and the noise seems to be coming from the catalytic converter??? I poked my head all around underneath the engine/trans. I even opened the rubber cover over the clutch lever so I could look inside and see if anything was amiss. As best I can tell, the rattle is coming from the Cat.

To me this is very strange, since there are no moving parts inside. The sound is a regular rattle, like a vibration hitting the harmonic of a heat shield. However I pushed on every heat shield underneath the car and the tone never changed.

I tried to get a video showing the location of the sound, but as the car warmed up it started to go away. It seems most prevalent when things are cold, or are very hot, as it at the end of a charge down the dragon. Once it sits for about 3-5 minutes, the noise seems to go away. I may the video again later if anyone feels it would help.

So I'm at a total loss. I'm going to have to take the car to the dealer (still 8 months left on the warranty ) I have a feeling. I'm just not looking forward to the battle that will ensue over the aftermarket clutch. It'd be nice if I could figure this one out before I take it in.



As always, any help is greatly appreciated...

 

I am willing to bet that your honeycomb broke inside of your cat. That is what happened to me. The longer it goes the more it will rattle, and If you wait long enought it will break the tip off of your 02 sensor and then that will have to be replaced. If it is not the heat shield like you said im sure it is this

 

djpeak: Thanks a bunch. This confirms what some guys at work were telling me. I just never expected something like that could happen under "normal" operating conditions. It's good to know I'm not the first S2000 to have this problem though...

Taking it to the dealer this evening; this will be warranty claim #4 I believe.

 

yeah you have 80k miles on the cat so you will be good, keep us posted on the situation but i am almost positive that is your problem.

 

Make sure the dealer doesn't see any mods. This is pretty unusual. It normally means a manufacturing defect or that the mixture wasn't right.

They don't have to warrant it if mods are what broke it (or if they think the mods did it). I wouldn't mention any non-stock parts that they can't see like your clutch.

 

My cat honeycomb came loose and sheared off my 2ndary o2 sensor about 2 months before it started rattling. Once it started, it only got worse.

 

Thanks for the responses guys. I dropped off the car today at the dealership, but it was end of day so they won't look at it until tomorrow.

As far as mods, the only ones I have that would affect the exhaust temp/mix are... well... none.

The clutch should have ZERO effect on the catalytic converter and they'd have a very difficult time proving otherwise. I'd love to see them try to fight me on those grounds. Otherwise it's just some carbon fiber bits (front splitter, rear wing, radiator plate), K&N drop in filter, and Muz front chassis brace. If this isn't an in-and-out replacement (assuming cat is the real problem - at this point I can't think it would be otherwise) then Honda Customer Care and I are going to be having a very long discussion.

djpeak: are you saying the service life on the cat is 80,000 miles? that's actually less than I would have expected, but thanks for the info. Car is only at 26000 right now so they definately can't complain on that front.

 

Do not rush into the honeycomb theory.....your o2 sensor may have wiggled itself loose and is rattling in its bung. This is a 5 min fix if it is. I had a invidia test pipe installed and i had the same rattling, it ended up being the o2 sensor wasnt torqued down right, and was bouncing around in its bung. It could JUST as well be your honeycomb, but i would just make sure its not your o2 sensor, or heatshield first oi!

 

well he dropped it off at the dealer so they will tell him whats up.

 

I checked basically everything while I was under the car, so I don't think it was the o2 sensor. Thanks for the tip though, definitely something to watch for; but since it's all as installed from the factory i'd be very surprised to see that it's loose.