Cylinder Four Cooling ModCooler Temps, Smarter Power Cylinder 4 Cooling Mod for EJ EnginesThe EJ engine is tough, but not perfect. One of its known weak spots? A coolant flow dead zone near cylinder 4. That hot spot can lead to uneven temps, knock, and even detonation especially in tuned or track driven Subarus. This cooling modification kit fixes the issue by redirecting coolant through that neglected passage, allowing it to recirculate and flow evenly throughout the system.