Rattle in Cat?

[CorSVXette]

I getting vibrating/rattle that sounds like it is comming from the cat. I only rattles at around 1800-2000 rpms then goes away. so I hear every time it shifts. It seems it only does it after it warms up after 5 min. or so. Anybody had this problem?:(

[benebob]

Originally Posted by Paul

I getting vibrating/rattle that sounds like it is comming from the cat. I only rattles at around 1800-2000 rpms then goes away. so I hear every time it shifts. It seems it only does it after it warms up after 5 min. or so. Anybody had this problem?

Everybody has or will have this problem. Sometimes its the heat shields. They can be removed or repacked with fireproof insulation. Other times its the cat or resinator breaking apart.

[redsvx]

Had the same embarrasing vibration/rattle when I bought the 94 ...
Elite Stainless Exhaust muffler shop cut out the resonator and welded a straight pipe in
All for $30

[YourConfused]

rattle = subsrtait or heat shield

[AlcyoneDaze]

I removed the heat shields and repacked them with strips of heat wrap, the the type racers (and some ricers ) put around their headers - problem solved. Model rocket wadding, found at a hobby store should also be effective if you want a cheaper option

[PaulDexler]

I have exactly the same heat shield rattle. I was going to take the car to the dealer to have it fixed (the local dealer claims they have a couple of techs who worked on SVXs since they were new), but maybe I'll just take it to my local muffler shop. (One mile drive vs. 25 mile drive to the dealer.) Mine comes in at about 1500 rpm, and gets less as the car warms up. It never goes away completely, however. There's always something...

[svxistentialist]

Originally Posted by PaulDexler

I have exactly the same heat shield rattle. I was going to take the car to the dealer to have it fixed (the local dealer claims they have a couple of techs who worked on SVXs since they were new), but maybe I'll just take it to my local muffler shop. (One mile drive vs. 25 mile drive to the dealer.) Mine comes in at about 1500 rpm, and gets less as the car warms up. It never goes away completely, however. There's always something...

Paul,

This rattle could be the heat shield, but maybe not. If the fix above does not make the rattle go away, then the cause is very likely to be loose baffles in the resonator. That's what it was in mine.

I did the straight pipe insert fix, and did not like the sound afterwards, it was coarse.

A new resonator is expensive. If it's the resonator, cut it out and cut it open. Tack weld or solder the loose plates. Stitch it all up again and weld it back in place. No more rattles.

[Mine use to rattle, fizz and buzz at around 1700 rpm, I think]

Joe

[CorSVXette]

Thanks for all your ideas on what the problem is. It appears to be a common problem with these cars. I will climb under there and see what the problem is. Is there anyway to tell where it is comming from when I get under there?
ps. "Yourconfused" said "rattle = subsrtait or heat shield" What is "substrait"?

[svxistentialist]

Originally Posted by Paul

Thanks for all your ideas on what the problem is. It appears to be a common problem with these cars. I will climb under there and see what the problem is. Is there anyway to tell where it is comming from when I get under there?
ps. "Yourconfused" said "rattle = subsrtait or heat shield" What is "substrait"?

If you climb under, you may find that a heat shield is loose. Heat shields will be above the exhaust components. They are fitted in an attempt to stop unwanted heat leaking into the cabin.

If one or more is loose, what can happen is they will vibrate in unison with the exhaust, as the exhaust is bolted straight onto the engine, and vibrates when the engine does. [In scientific terms, this is called sympathetic vibration ]


This is the first job you must do, ensure nothing is loose and able to rattle.

If it still makes a noise after you have secured all the heat shields, then it is very likely you have loose internal baffles in the resonator.

Proceed to fix as outlined above.

Joe

[redsvx]

Originally Posted by Paul

Thanks for all your ideas on what the problem is. It appears to be a common problem with these cars. I will climb under there and see what the problem is. Is there anyway to tell where it is comming from when I get under there?
ps. "Yourconfused" said "rattle = subsrtait or heat shield" What is "substrait"?

You should just take it to a muffler shop and tell them to take out the center resonator. You don't need the resonator anyway.
Go to a shop that does Stainless and have them weld a Stainless pipe in there. The guy at the shop told me the SVX exhaust is Stainless.

Try that first. It's the easy fix.

[svxistentialist]

Originally Posted by redsvx

You should just take it to a muffler shop and tell them to take out the center resonator. You don't need the resonator anyway.

Try that first. It's the easy fix.

It certainly is the quick and easy fix, but you are assuming that it is the internal resonator baffles. There have been many people on the Network who had loose heat shields. Tightening them up stopped the rattle.

If you cut out the resonator, and the rattle is actually heat shields, it will still rattle with the stainless pipe.

And the resonator was put in there in the first place to control the gas velocity and give higher torque in conjunction with the engine scavenging system. If you take it away for no good reason, the car will still work OK, but not as the engineers designed it.

And it will sound awful.

My 2c.

Joe

[PaulDexler]

As I said in my earlier post, I was going to try my local muffler shop about the heat shield problem. The guy there has done good work on my other cars, so what the heck, right? I took it in to him about 2:00 this afternoon. Happily, there were no other customers. He put the car right up on his lift, and heard the problem as he drove it on. After raising it, he tapped on the two pipes. The right side was fine, the left side clanked a lot. He rooted around a bit, and found that one of the four bolts holding the heat shield in place was missing. He found a bolt in his parts box and put it on. Much less clank. Then he noted that there was a bracket that was loose. He fired up his torch and re-welded it back on. Then he pried around with a large screwdriver to move anything else that might be touching. When he was satisfied, he said I owed him $10, and I drove the car off his lift, reveling in the fact that it was quiet at last. $10 well spent. He said he had a customer, a woman who with her sister, had identical cars. He tweaked the system for his customer the way he did mine, and charged her $10 also. The sister went to the dealer, who replaced half the exhaust system, and charged $300. His comment was that most of the people at dealerships only know how to replace parts, not how to fix things.

[CorSVXette]

Originally Posted by PaulDexler

As I said in my earlier post, I was going to try my local muffler shop about the heat shield problem. The guy there has done good work on my other cars, so what the heck, right? I took it in to him about 2:00 this afternoon. Happily, there were no other customers. He put the car right up on his lift, and heard the problem as he drove it on. After raising it, he tapped on the two pipes. The right side was fine, the left side clanked a lot. He rooted around a bit, and found that one of the four bolts holding the heat shield in place was missing. He found a bolt in his parts box and put it on. Much less clank. Then he noted that there was a bracket that was loose. He fired up his torch and re-welded it back on. Then he pried around with a large screwdriver to move anything else that might be touching. When he was satisfied, he said I owed him $10, and I drove the car off his lift, reveling in the fact that it was quiet at last. $10 well spent. He said he had a customer, a woman who with her sister, had identical cars. He tweaked the system for his customer the way he did mine, and charged her $10 also. The sister went to the dealer, who replaced half the exhaust system, and charged $300. His comment was that most of the people at dealerships only know how to replace parts, not how to fix things.

Man! $10.00!!! How I wish I lived in California right now!

[YourConfused]

A little late, but I meant to say the internal structure in the cat that can come loose and rattle. It's an annoying noise like you described. fixt fo 10 bucks! good for you.
p.s. stainless

[redsvx]

Originally Posted by svxistentialist

It certainly is the quick and easy fix, but you are assuming that it is the internal resonator baffles. There have been many people on the Network who had loose heat shields. Tightening them up stopped the rattle.

If you cut out the resonator, and the rattle is actually heat shields, it will still rattle with the stainless pipe.

And the resonator was put in there in the first place to control the gas velocity and give higher torque in conjunction with the engine scavenging system. If you take it away for no good reason, the car will still work OK, but not as the engineers designed it.

And it will sound awful.

My 2c.

Joe

Mine was the resonator ... and you're right it doesn't sound that good.
Next I will put an aftermarket resonator in there and a flowmaster muffler.
I fixed it quick cuz I just couldn't stand the darn embarrassing rattle.