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-I recently put on a random tech cat and Greddy cat-back. Eventually, all was working well until I noticed that whenever I run over a puddle, I notice this loud, clanking vibration that sounds like it is coming from the front of my exhaust / the cat. The sound also gets much tinnier and basically sounds like crap. This happens immediately after I drive through a puddle, and takes about 2 min of driving before it is back to sounding normal. Again, it happens EVERY time I drive through a puddle. It hasn't really rained here in Cali for quite a while, so I'm dreading the first rain. Anyone have any ideas what this problem can be? Do I not know something about Hi-Flow cats? Thanks

 
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This is normal and is called thermal shock.

When the exhaust is hot the metal expands, when it suddenly hit cold water it contracts rapidly and will need a minute or two to return to normal.

When it rain water hits it all the time and this will not happen unless it is slightly submerged in a puddle

 
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Yeah, i have the random, and a apexi N-1 and it does the same thing.

 
Rep Power: 298

known problem... happens with stock setup.

 
Rep Power: 258

yeah i have the same problem and have a stock exhaust. the car shounds soo ghetto from the outside