Please help me with some ideas for diagnosing and fixing what I think is my heat shield rattling. I have searched through all the threads on rattles here and on MINI2, and have tried all of the known fixes to no avail.

My symptom is this: a metallic rattle from underneath the car. Not too loud inside, but loud on the outside. It happens most often when the car is idleing around 1200 RPM, and not at any higher or lower engine speeds. The sound is not very solid...more tinny...so I think it's the heat shield. It happens more when the car is hot, but can also happen occasionally when it's cold. It happens whether or not the A/C is on. I have checked all of my exhaust connections and clearances and they are fine. All of the heat shield nuts are tight.

My latest idea: I did notice that when I tap on one piece of the heat shield under the car, it seems to vibrate and make a bit of a buzz very briefly. My theory is that it might be resonating and causing the problem. Has anyone else experienced this?

I'd like to temporarily shove some sort of material up under this part of shield (rubber maybe) to see if I can dampen and prevent it's vibration. Does anyone have any idea what kind of material would be safe to put against the shield (on the side opposite the exhaust pipe) to dampen its vibration?

If this does prove to the be problem, I was thinking a fix might be to line the car-side surface of this piece of heat shield with silicone caulk so as to (1) fix it more solidly against the car body and (2) add sound-dampening mass to the shield. Silicone II brand caulk is rated for up to 400 degrees F. Does anyone know how hot the heat shield gets? Do you think this would work okay?

Thanks in advance for any advice on these questions! :smile:

 

Some wadded fiberglass insulation would work as an experiment.

 

Do you have a heat shield behind and up the exhaust manifold? If so, that may be it. It can be removed and chucked. Newer cars don't come with them...

 

Did you figure it out? I have a sound I'm ready to atribute to some part of the heat shield also and wondering what you found.

 

...... could also be the internals of the Catalytic Converter.

 

I had the exact same sound-not a heat shield but the catalytic converter. A little tightening & the problem was fixed.

Lois

 

I am still working on mine, stuffing fiberglass insulation wads here and there under the heat shield to isolate the problem...with no luck yet.

I also found an aluminum-shielded cable, about 1 centimeter diameter, exiting from under the heat shield and noticed that its shielding is getting marred from vibration against the edge of the heat shield. Next time I'm under the car I'll try fixing that by cutting away some of the shield.

Lois, what exactly did you tighten to fix the rattle from your cat?

Thanks
- Mark

 

Unfortunately, I took it to the dealer to find the noise & they found it in about 5 minutes. The mechanic told me it was a loose connector on the cat. He put a wrench to it & tightened it. No problem since.

Lois

 

Thanks. I'll take another look at the bolts on the cat while I'm down there next time, but I'm pretty sure I checked that already and mine are tight.

 

How can you tell if it's in the internals? Is there some way to test for that?

 

OK, sounds weird, but I have heard that if you place heavy magnets on the Cat. that can stop the rattle. If you have any magnets, then give it a try.

Otherwise you'll have to have a shop look at it I guess.

 

I Had The Same(maybe) Problem. They Are Replacing One Of The Exhaust Resonators.

 

i have the same problem recently. Seems to happen after the car has warmed up, like if i went out then stopped at the store. When i come back out and take off, that's when i hear it. It's a hollow vibrating metal sound that gets louder with the rpms and goes away when the clutch is depressed. Seems to only happen when the engine is under load and the car is in gear moving. I tried to duplicate it while standing still and can't. My exhuast is custom made from magnaflow parts.
If this is the cat, what is the cost for a new one and do I have options or does it have to be an oem cat?

 

IF it is the cat then I would try the magnets first. Otherwise the way I see it is that the cat is built into the header system and is not a bolt-on rplacement part. I will have to look more closely though as I have my stock system up in the shed. If this is true then to replace the factory cat you will have to replace the whole header.

One option is to by a used header from someone that has replaced theirs with an aftermarket, like myself (though I don't know that I want to sell mine).

Second option would be to go to the dealer and see what there solutions would be, i.e. replacement cost of a new header.

Third would be to by a good aftermarket header w/cat like the Milltek. Expensive option though, but I wouldn't be surprised if replacing the factory cat would be any cheaper, unless of course you are still under warrantee.

(I don't know whats up with this BOLD font thing!!! Arrrggg)

 

Tap around the can with a rubber mallet. If it rattles inside...

 

I'm still working on it, but found out something interesting since the weather turned much cooler here in the last week or so: the rattle happens less often and is not as pronounced as it used to be during my daily commute, now that my car is not running as hot.

Weird.

 

Just had my Miltek resonator replaced by Stratosphere for free after 9 months due to rattle inside. I thought i had heat shield issue but tapping on resonator revealed something inside rattling, called Stratosphere and they shipped out new one and will pay for return of my defective one. Said they a few similar cases. I'll put new resonator on next week.