The following study used data made available to CarBeast, provided by our data partners.
Many choose luxury brands like Lexus for the smooth, quiet rides that they offer and are willing to pay extra for this higher ride quality. But the 2016, 2017, and 2018 Lexus ES may provide a surprisingly noisy ride due to a loose muffler heat shield. As of this writing, there appears not to have been a recall initiated for this common issue.
Exhaust heat shields are thin sheets of metal that help to dissipate the heat generated by internal combustion engines. They are generally positioned on the underside of the vehicle between the exhaust pipe and the body of the car, and they prevent damage to the body and other components that could be caused by the high temperature of the exhaust gases, which can reach nearly 1000° F. Some heat shields are situated underneath the exhaust system, and prevent problems from spreading, such as unexpectedly lighting dry, flammable grass on which a vehicle might park.
If the heat shield is loose, it is usually identifiable by the rattling noise that it makes, and the noise worsens when the vehicle goes over bumps. A heat shield may come loose due to rust, which may also affect its bolts or weld fasteners. Rusting may happen faster on a heat shield due to high temperatures speeding up the process. A loose heat shield is mainly an annoyance, since it can usually still dissipate heat effectively even when loose. But if it is not repaired, a heat shield may completely detach from the vehicle, which can cause more problems, from melted wires to excessive heat in the cabin.
The 6th generation of the Lexus ES covered the model years from 2013-2018 and had either 3 or 4 underbody heat shields. For most of these years, the failure rates of the heat shields was completely average, but starting with the 2016 model year up until the 2018 model year, the heat shield on the muffler began to come loose at a much higher rate.
The cost to replace a loose exhaust heat shield in 2023 is usually around $223 for a Lexus ES, though the reasonable range can vary between $160 and $266. This can, of course, depend on a number of different factors:
To dig deeper into this problem, let’s look at what insights are available from CarBeast’s data.
CarBeast uses real automotive repair records from locations across North America. When a technician inspects, diagnoses, or repairs a car, they document the state of the car and any actions that they took. The CarBeast database contains hundreds of millions of these repair records for all different types of cars. The following image shows snippets of two actual repair records for the Lexus ES where the exhaust heat shield was replaced:
CarBeast regularly receives repair records like this from our data partners. The repair records are anonymized to remove any personal information about the vehicle owners. With such cleaned records, unique language understanding AI automatically recognizes thousands of different components, symptoms, and actions from the text. The image below shows an example of the concepts that are extracted from a repair record:
CarBeast includes two applications: CarBeast Foresight, which provides a future repairs forecast, and CarBeast Insight, which suggests best fixes for car problems diagnosed from symptom descriptions.
CarBeast Foresight presents a list of the repairs that are most likely to occur in the next 50K, 100K, or for however many miles selected to view a forecast. The list usually includes some repairs, such as replacing the tires or the brake pads, that are likely to occur for every car. But many of the items in the list will be repairs that are specific to the make, model, and model year of the particular car for which the forecast is provided. Foresight uses a hazard ratio to measure how specific a repair is to a particular type of car. In simplified terms, the hazard ratio measures how much more likely a Lexus ES is to require a specific repair as compared to an average car. The hazard ratio for muffler heat shield replacement on a 2017 Lexus ES is 61, which means that a 2017 Lexus ES is 61 times more likely to require replacement of their muffler heat shield than the average car.
The figure above shows part of the Foresight report for a 2017 Lexus ES. While the probability of needing to replace the heat shield is 4%, it is still much higher than for the average car. In other cars, this probability is the much smaller fraction of 1%.
Foresight also lets us learn more about when this repair may be required. As seen in the image below, most of the heat shield replacements occur fairly early in the vehicle’s life. Half of all Lexus ES muffler heat shield replacements have occurred between 37K and 76K miles.
This is also seen in the following chart that shows the mileages where heat shield replacements are required. Again, the heat shields appear to fail relatively early in the car’s lifetime, suggesting possible defects in the heat shield or its installation, rather than the heat shields simply wearing out with age.
In CarBeast Insight, a narrative description of symptoms encountered for a vehicle is input, and CarBeast’s AI automatically understands the description. The AI then suggests repairs that are most likely to fix the diagnosed issue. In the example below, “exhaust is rattling” is input for a Lexus ES, and replacement of the muffler heat shield is the third most likely fix suggested for the issue, under two other common Lexus ES repairs that also often result in the exhaust rattling.
CarBeast Insight provides related repairs that may be required when the heat shield is replaced. The list of related repairs below shows several different exhaust repairs:
The above observations suggest that rust/corrosion may be playing a role in the muffler heat shields failures, since rust and corrosion are often the cause of the other exhaust parts requiring repair. A look at the geographic breakdown of these repairs lends further credence to the rust possibility.
There is a lot of data in this chart, but the important information can be found by comparing side-to-side blue and orange bars (each state has blue on the left and orange on the right). The blue bars represent the share of Lexus ES ownership in each state, while the orange bars represent the share of heat shield replacements in each state. If the geographic location of the car had no relationship with this repair, there would not be much difference in the height of orange and blue bars. Instead, the heights are quite different in many cases.
Starting from the left, it’s clear that there are many of Lexus ES’s in California, but very few muffler heat shield replacements. The same is true for Florida and Georgia, but then in Illinois, the share of repairs in much higher than the ownership share. Going further across the chart, a pattern becomes clearer. Here are the states with the highest heat shield replacement rates as compared to their ownership rates:
These are mostly states that see significant snowfall in the winter, and so the use of road salt to melt snow could be contributing to accelerated rusting and corrosion of exhaust components, including the muffler heat shield.
In addition to the CarBeast database, evidence of this problem is also available from other sources. Club Lexus is an online forum for Lexus owners to discuss their vehicles. There are several posts on Club Lexus from owners experiencing problems with their muffler heat shields. The images below show some of the complaints:
As of March 1, 2023, there does not appear to be any recall associated with this problem, at least based on recall information at the National Highway Traffic Safety Administration (NHTSA) website. NHTSA may not issue a recall for this in the future either, given that a loose heat shield may not constitute a safety issue. So for now, Lexus owners may need to shoulder the $160-266 cost for this repair.
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