buzzing like a loose heat shield but not? - TCCoA Forums
 
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post #1 of 11 (permalink) Old 05-15-2015, 03:38 PM Thread Starter
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buzzing like a loose heat shield but not?

1995 T-Bird LX 4.6, 92,000 miles, garaged, original owner. Exhaust is factory original. At certain RPM's I hear a sound like a loose heat shield, but I can't find any bad welds or anything hitting the shields. So I took it to the local tranny guy here (who races on the local dirt track on the weekend) and happily he said, nope, not a tranny problem, something in the exhaust, and BTW, you have a very nice clean 20 year old car here, last of the Mohicans . What else besides heat shields causes this kind of noise? Hangers seem to be okay. Are there internal baffles in the factory muffler or resonators that fail after 20 years? The noise is a little embarrassing driving down the road.
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post #2 of 11 (permalink) Old 05-15-2015, 04:22 PM
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My 94 had some kind of ID tag that was spot welded on the driver's side cat that fell off and was jiggling around on top of the heat shield. My 97 did the same thing but I didn't spend time to isolate the issue before I replaced the exhaust pipes. I imagine it'd have be the same thing...

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post #3 of 11 (permalink) Old 05-19-2015, 04:54 PM
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the cats themselves?
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post #4 of 11 (permalink) Old 05-20-2015, 03:47 AM
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X2 on bad catalytic converters. Mines have been rattling for years now as I took it to trans place and was told the same thing. My Navigator also did the same thing as I replaced them with Magnaflow cats and all was well again. My Navigator was the one that had bad performance behind the converters being bad but the Tbird feels fine just noisy until the cats heat up. I could also smell the honeycomb inside the cat burning for about two or three weeks after it first happened.

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post #5 of 11 (permalink) Old 05-20-2015, 09:21 AM
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X3 on cat cons.

By the time you get the noise, the cat is 90% empty and there is one piece that can't get out, and is bouncing around. Replacing the cat doesn't always eliminate the noise, sometimes there is a piece in the muffler.

Al

97 T-Bird LX 4.6 - 80k miles
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post #6 of 11 (permalink) Old 06-03-2015, 06:05 AM
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Had the rattle issue on one car at exactly 1400 RPM. Loose heat shield on the Passenger side cat. Poorly placed spot welds allowed just enough of a gap to rattle cold and to rattle less once they were warm. In my case the cat substrate was fine. No other rattles. A long stainless band clamp from a diesel truck air intake wrapped around the heat shield and tightened up compressed the heat shield against the converter shell just enough to to stop the rattle without deforming the heat shield. My memory is that the spot welds are in a recessed channel in the heat shield and not conductive to being re welded. And as I recall the converter shell and the heatsheild are two different types of stainless. So trying to weld the relatively shiny heat shield to to the relatively scaly converter shell was just as likely to blow a hole through both.

If you can isolate it to the heat shield and it's a definite rattle at a specific RPM try a large band clamp. I'm talking the giant hose clamp style. Not the wide muffler clamp style. Any truck supply store or Napa should stock these. They are probably a bit big for AutoZone O'Riellys etc.

This might help someone. And depending on your heat shield it might take two.
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post #7 of 11 (permalink) Old 06-03-2015, 10:24 AM
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Quote:
Originally Posted by theterminator93 View Post
My 94 had some kind of ID tag that was spot welded on the driver's side cat that fell off and was jiggling around on top of the heat shield. My 97 did the same thing but I didn't spend time to isolate the issue before I replaced the exhaust pipes. I imagine it'd have be the same thing...
Mine too, one of the first "fixes" I made to my car was yanking that piece out with pliers

-Matt
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post #8 of 11 (permalink) Old 06-03-2015, 11:36 AM
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Ever since I went back to the factory exhaust set-up on my truck..When ever I'm backing into a parking space, or going through a drive through..

The exhaust makes a weird vibrating/buzzing sound like there's too much back pressure now..It sounds like the whole exhaust system is shaking..

It only makes that noise when I'm just barely crawling along though..If I'm driving down the street it doesn't do it..

I haven't noticed any loss in hp either..

What are your guys thoughts??..Ever had this happen to you before??







Rayo..

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post #9 of 11 (permalink) Old 06-03-2015, 02:13 PM
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I just solved the same thing today. There was a part number tag welded to the resonator. It had come loose and was inside the resonator head shield. I slid it to one of the openings in the head shield and pulled it out with pliers.

Nick
97 LX 4.6 - stock
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post #10 of 11 (permalink) Old 06-05-2015, 09:41 AM
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I had that problem too but mine was the heat shield behind the brake rotor... I have also had the cat problem before as well. That is the reason the slut no longer has cats.

Blake

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post #11 of 11 (permalink) Old 06-05-2015, 02:44 PM
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The cat con rattle is the worst, sounds like the car is falling apart.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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