Heat shields in vehicles are essential for maintaining safety and automotive function. The engine bay temperature can reach 220°F, which can be hazardous if parts are not protected by a heat shield. If a heat shield fails, this severe heat can melt the engine’s plastic parts or burn passengers’ feet as it travels through the vehicle. Furthermore, if the heat is not contained it can also burn nearby grass or plants, potentially starting fires.
This post covers heat shields’ various forms and functions.
What is an Automotive Heat Shield?
Heat shields, as the name implies, work as a thermal barrier protecting the vehicle’s components. Both the vehicle’s engine and the exhaust system become incredibly hot during normal use, and this heat would damage adjacent parts if it were not managed. In the exhaust system, heat shields protect the muffler, exhaust pipes, catalytic converter, and exhaust manifold. The catalytic converter, in particular, reaches very high temperatures. In the engine bay, turbochargers, header manifolds, and the radiator are shielded.
While the engine does get incredibly hot, its cooling system is largely responsible for regulating that area’s temperature. However, the gasses that the engine generates have to escape somewhere, and it is for this reason that the exhaust pipes are so hot.
Heat Shield Material
There are two main types of heat shields: stiff, and flexible. Stiff heat shields can be made of steel, but aluminum is preferred as it is a lighter material. Stiff shields are mechanically fastened to the substrate they are shielding, attached with bolts, nuts, and rivets. Flexible heat shields are lighter, made of aluminum instead of steel, are more conformable, and can easily be taken off.
Traditionally harder, thicker metals were assumed to be better at spreading heat, but advanced thermal coatings have allowed engineers to use many different materials for heat shields. This modern technology makes flexible heat shields a compelling choice, especially when their performance-enhancing lighter weight is taken into consideration.
“Peel and stick” flexible heat shields have an adhesive backing, can be cut and easily adhered to a variety of substrates, and are lighter weight than stiff shields. They are often made of woven silica or composite glass on the adhesive side, with aluminum coating on the heat-reflective side. These shields work well under the hood, among other applications.
Overall, heat shields protect better against heat than adhesive heat shield tape. Heat shields enable more cooling, and because heat causes a horsepower reduction, shields can provide extra horsepower. Perhaps surprisingly so, mechanically-fastened heat shields can weaken over time and tear at the attachment site. Adhesive shields, in contrast, spread out the load of attachment evenly and are less susceptible to this weakness. In addition, galvanic corrosion can ensue between the steel fastener and aluminum heat shield.
Adhesive Heat Shield Tape
Heat-reflective tape is highly conformable to irregular surfaces, and useful for wires and pipes as well as larger parts – such as a stiff heat shield. As the name implies, heat shield tape works by reflecting heat away from the substrate it is attached to. Aluminum foil is popular metallic backing for the tape, due to its high conformability, high thermal reflectivity, and low emissivity. Emissivity is the measure of how much infrared energy a material emits, or, in other words, how much thermal energy it releases.
Manufacturers use glass fiber to create woven layers. Aluminum foil then coats these layers, making the tape highly effective—it can withstand up to 572°F and reflect about 80% of incoming heat. Lamart’s 892L aluminum tape is an excellent heat-reflective wrap that performs well in high-temperature environments.
Signs of a Failing Heat Shield
Heat shields are made to last the car’s lifetime, but they can fail. With firm heat shields, their attachment points can rattle loose over time. An annoying rattling sound signals this problem, caused by the heat shield moving around. Another clear sign is a burning smell; if the heat shield is malfunctioning, unprotected parts can melt, releasing a prominent odor. Unusually high temperatures in the engine bay, as well, could indicate problems with the engine cooling system or a heat shield issue. An engine hood that is untouchably hot is another warning sign.
If your exhaust is rattling, the easiest fix is to tighten the heat shield’s hardware. If this isn’t possible, you can weld the heat shield to the exhaust—but without caution, the heat shield and the exhaust pipe could burn through. If the old hardware is damaged, installing new nuts and bolts is another option, as is using stainless steel screw clamps or ties.
Heat shields and other heat shielding materials are essential to maintain the safety and function of your vehicle. Our experts work with your team to make sure our solutions are tailored to your project’s needs. Contact Lamart to find heat-shield and other insulation solutions tailored to your automotive needs.