A burning smell coming from the engine.When the heat shield is damaged, one of the first symptoms is typically excessive heat from the engine bay–heat that can cause peripheral parts to melt. As the heat shield becomes more damaged, it won't properly contain the high temperatures and direct them out through the exhaust, leaving surrounding parts of your engine vulnerable to damage. If the temperature becomes too extreme, it can warp or melt plastic parts of the engine, or cause belts to break. If you start to notice a burning smell coming from your vehicle, or observe that the hood of the engine is too hot to touch, you should make an appointment with your mechanic as soon as possible.
Rattling or scraping noises.A rattling exhaust can be both annoying and nerve-racking. If the heat shield becomes loose or broken, it will begin to vibrate and might produce a rattling sound. It could simply be that the hardware is loose and needs to be tightened up. But if rust or other damage is causing the heat shield to deteriorate your engine is in danger of overheating.
If the engine overheats too much, you might even find melted plastic parts under the hood—all because of the failing heat shield.