Do any of you with the random tech cats have a weird hissing/rattling noise coming from them? I'm certain it's the cats making the noise and one seems to be louder than the other. I had my borla H pipe welded, put exhaust cement on every pipe connection, put dynamat on all of the heat shields, checked all of the exhaust clearances and the sound is still there. It's not very loud and I hear it most while decelerating but it’s present at all RPMs. If I push in the clutch while moving the sound goes away. I also hear the sound if I just rev it in neutral so I know it's an exhaust noise. One of my buddies had a high flow put on his cavalier and it made a similar but louder sound. But, the installer had dropped his cat from about 7 feet onto a concrete floor before installing it. I got the cats from Jeff @ performance Nissan and he'll take care of me if they are in deed defective but I just wanted to be sure before I go through the arduous process of un/reinstalling the cats.

Thanks,
Mike

 

It sounds like they didn't get a good seal where they meet the y-pipe. I put a set on for a friend and had a leak at first, It took a couple tries to get them on securely. Had to remove the y-pipe rear connection and tighten the front first.

You might want to put your car on jackstands and then get under it and feel around for an exhaust leak with it idling (do it when the engine is cold, it gets hot quick!)

 

I don't have a Y-pipe, I have the borla dual And like I said I've sealed every connection from the cats back with exhaust cement. I've been under my Z several times since to verify that there are no leaks, the cats have been on for about 2 weeks. I've even used a spray bottle with water to spray on all of the joints while it's idling and didn't find any leaks. I guess my question is, is it normal for the high flow cats to sound like this? Maybe I'll just take my Z to a muffler or speed shop and see what they think. Thanks for the reply though. Any others

 

Sometimes high flow cats have a kind of hissing sound....this is just your exhaust gas moving through the cat element though...if you have a rattle it could be a loose heat shield, part of the exhaust/cat coming in contact with another part of the car, or a broken cat element (honeycomb). Hope this helps.

 

Yeah it does have a hissing sound which I thought was normal like you said. But the last part of your comment is what I'm thinking it is; a damaged honeycomb.

Thx

 

The random h/f cats were poorly designed for our car. They actually lower the exhaust nearly an inch. When I installed the cats they sat on the X bar and made the worst noise you can imagine. I bought my pipes through Jeff also thinking that random had the best design. I'm not convinced. I tried the washer trick that Jeff's mechanic (Rocky) told me about but it didn't work. The cats still hit the X bar over bumps. I have since removed the X bar and have elinimated most of the noise. I still hear a funny vibration coming from the passenger cat where it connects to the Stillen exhaust. I emailed Jeff a week ago but have yet to hear from him. I also think it stinks that the pipes do not come with any of the hardware, IE bolts, studs, gaskets etc.

 

The sound I'm hearing is coming mainly from my passenger side cat too. It sounds exactly like a rattle snake. I was driving around last night with the windows down getting a good listen to it. I'll give it one more try this weekend to see if I can find any leaks, if I can't I'll be positive it's the cats.

 

This seems to be a problem with any cat replacement; I have the Kinetix bypass pipes and they make a similar noise, others experience as well.

 

I just put in my headers catless connected to the Borla TD and have the same rattle sound like you described. To be sure there is no leak, I check the exhaust connections again and welded them. But the sound still there. It's annoying sound when you step on the gas.
You guys think it's rubbing against the car or catless is creating that rattling sound?