Dynomax rattle?

[SimpleGreen]

Anybody heard anything out of the ordinary from there Dynomax VT mufflers?

I swear I think one of mine (probably the driver side) has something loose inside of it. When I crank the car in the morning it has an on and off rattle under the rear end on the start up high idle, then it goes away when the car idles back down. It will not do it anymore until the car has sat for several hours and I start it up again. I have checked and all my clamps are VERY tight still and they are not touching the trunk floor or anything like that.

If I can narrow it down to one of the mufflers, I'm going to call Dynomax and see what they say. The only other thing I feel it could be is the heat shield under the center of the car, but the sounds like it's much further back.

[matt6589]

I don't hear anything like that with mine.

[SimpleGreen]

Originally Posted by matt6589

I don't hear anything like that with mine.

Yea, it may or may not be them. I'm going to put the car on the ramps this week sometime and crawl underneath and touch, pull, push, everything, lol. See if there is anything out of the ordinary.

[matt6589]

If it was something in one of the mufflers, why would it go away completely after the engine warmed up?

[SimpleGreen]

Originally Posted by matt6589

If it was something in one of the mufflers, why would it go away completely after the engine warmed up?

I've seen stranger things.

What's crazy about it is it will rattle the first time you start it. If you shut it off immediately and start it again, the car won't go into it's super high closed loop idle, and voila, NO RATTLE. What the hell? Lol. So then I have to wait a few hours again to try and hear it. I think the cold start high idle rev is just the right resonance to making something shake now (just started the last few days). Luckily it's non a consistent noise so it's not bothering me all the time, but it sure makes it hard to hunt.

[JohnnyBfromPeoria]

Mechanic's stethoscope only costs a few bucks... Have a helper start it when cold and listen at the muffler. Mine's so loud through the ear pieces, I can find or eliminate a sound in seconds.

John B.

[SimpleGreen]

Originally Posted by JohnnyBfromPeoria

Mechanic's stethoscope only costs a few bucks... Have a helper start it when cold and listen at the muffler. Mine's so loud through the ear pieces, I can find or eliminate a sound in seconds.

John B.

Not a bad idea. Thanks

[Henry G.]

Ok I got this: The LFX rattles and buzzs when you first start it, period. After about 20 secs it mellows out. My Dynomax mufflers were a butthair away from the body and this extras vibes made it hit the body. I loosened the clamps, then re-tightned them leaving more room, this time with an impact wrench on the lowest setting, problem solved. I still dont know why it runs rough for the first 20 secs, but at least the rattle is gone. It WAS BAD. It vibrated throughout the car!! Impact wrench and at least 1/2" clearance was the key.

[matt6589]

Hmm I haven't heard anything like this with mine. Is this something that you guys have had since the beginning of installing the mufflers or did it develop over time?

[Horriblecreation]

Originally Posted by SimpleGreen

Anybody heard anything out of the ordinary from there Dynomax VT mufflers?

I swear I think one of mine (probably the driver side) has something loose inside of it. When I crank the car in the morning it has an on and off rattle under the rear end on the start up high idle, then it goes away when the car idles back down. It will not do it anymore until the car has sat for several hours and I start it up again. I have checked and all my clamps are VERY tight still and they are not touching the trunk floor or anything like that.

If I can narrow it down to one of the mufflers, I'm going to call Dynomax and see what they say. The only other thing I feel it could be is the heat shield under the center of the car, but the sounds like it's much further back.

I swear I thought I was going crazy hearing this rattle when I started up my car.... Mine definitely does the exact same thing. Its a pretty "hollow" or "flimsy" sounding rattle for maybe the first 10 seconds or so when I first start her up, and then it goes away. I meant to get under my car to really narrow it down before I put her in storage, but now she's dormant for the next 10 months. Interesting to see someone else has the same issue though.

[SimpleGreen]

Originally Posted by matt6589

Hmm I haven't heard anything like this with mine. Is this something that you guys have had since the beginning of installing the mufflers or did it develop over time?

It only occurred within the last week or so. The exhaust has been on for nearly a month.

[SimpleGreen]

Update:

Rattle seems to last longer and longer each time I start the car.

Jegs is sending me a brand new system with a FedEx tag so I can send back the old one. Will be refunded as soon as they get the old set on hand.

Hopefully no more rattles...and the tips match.

[Billabongi]

Couldn't this just be the valve inside the muffler adjusting to the airflow on startup?

[SimpleGreen]

Originally Posted by Billabongi

Couldn't this just be the valve inside the muffler adjusting to the airflow on startup?

Negative. The exhaust sounded perfect for almost three weeks, then this rattle came out of nowhere. I don't think it's the valve. It sounds like some of the perforated metal inside is loose. If the new one does it down the road, I'm going to warranty it again and just buy Corsa like I should have did from day 1