Buckled, but downward, but how ???

OK, on my DW's B1500 with the 3.9L, I changed out the muffler back in November or December of 2005. Since that time, the van didn't have any issues. In the last month or so she has complained about muffler noise.

While poking around my B2500 and fixing the IAC issue, I took the digital camera and took some pictures under her B1500 of the muffler. Was I surprised to see something so strange, I still don't have a grasp to understand how this could have happened.

The muffler actually buckled downward. Downward??? I can understand upward if she hit something in the road. However, the buckled is more strange than hitting something in the road. Even the buckle line metal folds over itself. Is that wacked or what?

I even took a picture of the cat as well. It's fine without any issue. All the clamps and brackets are still in place with the exhaust system too. There is no play either. I tapped on both the muffler and cat. Those are still good. There is not a hole or crack in any of them either.

My question is, how did this ever happen, and if known how to prevent it from doing this again.

Looks like it might have backfired. I wonder if your exhaust valves are burnt. My 85's muffler did that and I had 3 badly burnt exhaust valves on the 318. I just did the heads on my 94 B250 with the 318 and the seats were bad on all the valves. I was amazed it ran as good as it did with one very low cylinder (#4 @ 60psi) but it did have a lobey idle and shuddered in OD @ 45 MPH.

A backfire or very extremely hot exhaust gas release maybe an answer to this. I can't understand any other causes for this to happen.

Some suggestions were getting backed into by a small car to push the tail pipe forward. However, the tail pipe exits out the side by the back wheel.

Got me thinking about the idle. It idles really smooth.

To me, it looks like stress or just an internal failure of the muffler. Was the muffler the exact same size as the original? Was this a "universal" type mufler as I see it's welded in. Check your motor mounts and tranny mounts. Bring the muffler back under warranty. All my mufflers are Walkers or Maremonts and have a lifetime warranty. Some others at least have a 1 year warranty.

Chump,

Thanks for the reply. Yes, it is an AutoZone "Universal" type muffler. It's the same size in general terms, but the inlet/outlet pipes are slightly in different locations.

The muffler isn't welded on. So, I should be able to undo the clamps and take it off. However, did you see the pictures of the clamps. Within 6 months they rusted! How cheap!

Thanks for your input. Your a wealth of good information.

Yeah, I see the rust, thats why I questioned it's quality. Probably what happened is the inlet and outlet being off a bit caused some excess stress and as the inside on the muffler gets weak, it buckled. Call around locally for a good muffler, compare prices and warranties. Walker, Maremont and Arvin brands are good. I've always used the clamps from NAPA. The mufflers there will be higher priced, though.
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