A car heat shield. Learn when to worry about a rattling heat shield.

How to Tighten a Rattling Heat Shield

For the most part, we associate a quiet car with a healthy car. Loose parts usually mean something is wrong, and could affect the reliability and safety of your vehicle. While some see a rattling heat shield as a mere annoyance, others may find it embarrassing. In some cases, a loose heat shield could be a major problem.

Because the primary purpose of the exhaust system is to route superheated gases away from the engine, everything around the exhaust manifolds, catalytic converter, exhaust pipes and muffler gets hot. Catalytic converters are particularly hot — they only begin functioning between 400 and 600 degrees Fahrenheit, and normally range between 1,200 and 1,600 degrees Fahrenheit. The rest of the exhaust system typically measures 300 to 500 degrees Fahrenheit.

Exhaust Heat Shields — What Are They Rattling For?

These heat shields were mounted to the body over the exhaust.Many car parts cannot manage such heat. Plastic and rubber parts can melt or become brittle, electric motors and sensors can fail, and dry grass or paper can spontaneously combust. Made of thin metal sheets, heat shields deflect much of the extreme heat, some affixed to the exhaust system and others affixed to parts needing protection.

Exhaust heat shields fail for a couple of reasons: rust and vibration. Fittingly, the parts the heat shields are designed to protect often cause their failure. All metal exposed to the atmosphere corrodes, but heat speeds up the process, so clamps, bolts or welds can rust to nothing, leading to a loose heat shield. Vibrations can weaken the metal, causing a heat shield to fall off, rattling against the exhaust or some other part of the vehicle.

How to Fix a Rattling Heat Shield

Some don’t see much use for a rattling heat shield, so they simply remove them and discard them, but this can be a problem. Because the heat shields are designed to protect other car parts from the extreme heat of the exhaust, removing them completely could cause premature failure of other components or even fire. The best way to fix a rattling heat shield is to replace it or reaffix it. Here are a few ways to fix your rattling heat shield:

  • Weld: If you have access to a welder, you may be able to tack the heat shield to the exhaust. Be careful, as both the thin metal heat shield and exhaust pipe may burn through.
  • Bolt: In some cases, you may be able to install new nuts and bolts to reaffix a bolt-on heat shield. If the holes are too wide, fender washers can make up for that extra space.
  • Clamp: Stainless steel screw clamps can be used in some situations, such as where a heat shield was welded or clamped to an exhaust pipe.
  • Tie: Another way to fix a loose heat shield is with a stainless steel tie, which won’t rust after installation. Link several together for larger components, such as muffler heat shields.

If a loose heat shield has you worried, you may not need new exhaust pipes, but one of these quick fixes can restore your sanity and protect your vehicle from the heat. Of course, if you’re going to get under the vehicle, be sure it is securely lifted and supported by jack stands.

Check out all the exhaust parts and accessories available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on heat shields, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

about author

Benjamin Jerew

Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.

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