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Muffler Discoloration: Normal or Not?

What's That Color?

Many mufflers undergo a moderate change in color – taking on a bronze or blue hue – after a period of operation. In most cases, this color change is perfectly normal, resulting from the varying temperatures within the muffler’s internal chambers.   

Bronze or Blue – a "Heated" Issue


Many mufflers feature several internal partitions designed to improve structural stability, enhance sound quality and extend service life. These partitions separate the muffler into chambers that contain exhaust gasses for varying lengths of time to reduce sound. As a result, some chambers will operate at higher temperatures than others. Under certain conditions, this can result in an uneven bronze or blue discoloration on the exterior of the muffler.

When is there a Problem?

In most cases, there is nothing wrong with the muffler – the color shift is a normal result of the unit's thermal characteristics. However, high temperature discoloration when accompanied with increased fuel consumption and elevated emissions could indicate an underlying engine problem such as misfires (possibly due to a fouled spark plug), which can increase the catalytic converter and muffler temperature. Service providers can simply test drive the vehicle while monitoring the misfire count with a scan tool.

Quiet-Flow SS Advantage

The 100% stainless steel Walker® Quiet-Flow® SS muffler is designed to resist rust-out more than three times longer than competing designs. Traditional mufflers use a shell made of two sheets of thin, aluminized carbon steel – one layer to seal the interior and another to cover weld points for a cleaner look. The Walker Quiet-Flow SS muffler uses a single, heavier-gauged, stainless steel wrap. This feature leaves the muffler less susceptible to corrosion and helps to better control sound. 


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The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.