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Mine explosion-proof diesel engines are critical for underground coal mining, yet the long-term performance degradation of their exhaust systems poses substantial risks to operational safety and environmental compliance—a gap not addressed in short-term performance-focused studies. This study investigates the degradation and failure mechanisms of dry, wet, and combined exhaust systems under simulated mining conditions using a JHP4105DZDFB-G engine. Experimental results show that the wet system exhibits the fastest degradation, with exhaust backpressure increasing by 15.2% within 500 hours of continuous operation under simulated mining conditions due to sludge accumulation, leading to a 12–15% power loss. In contrast, the dry system maintains lower emissions (NOₓ, HC, CO, and PM were reduced by 68.36%, 71.71%, 55.39%, and 82.28% compared to the wet system) but suffers thermal fatigue in condensers after 1000 hours. The combined system shows hybrid failures, with PM emissions exceeding regulatory limits (0.4 g/kWh) at 300 hours. Mechanistic analysis reveals that wet systems fail primarily due to mechanical blockage and corrosion, while dry systems succumb to thermal-mechanical fatigue. A multivariable regression model and machine-learning algorithms are developed to predict degradation thresholds, enabling proactive maintenance. Thermal management optimization for dry systems is proposed.