Overall, the 6.6-liter LML Duramax has proven to be fairly reliable throughout the years. However, this generation of the Duramax can have issues with leaking up pipes and faulty exhaust manifolds. +Read more
The 6.6 Duramax up pipe can crack and leak, leading to a loss of power, excessive soot along the firewall, and exhaust fumes entering the cab. In addition, as the exhaust manifold goes through numerous temperature changes during operation, its metal can become brittle and crack, causing leaks and louder exhaust noise. Symptoms of a faulty exhaust manifold include decreased fuel efficiency, poor acceleration, and a lack of power.
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