21148722
Filler Cap
Mack

The filler cap serves as a robust closure for coolant or fluid reservoirs in heavy-duty Mack platforms, delivering a reliable seal against contamination and pressure fluctuations. Built to withstand vibration, temperature cycling, and road debris, this cap maintains the integrity of the cooling system and prevents loss of coolant during high-load conditions. A proper seal minimizes evaporative losses and reduces the risk of air ingress that could lead to cavitation or inconsistent temperature regulation. The cap’s design also accommodates pressure relief characteristics that protect components from sudden spikes while allowing safe venting when required. When servicing cooling circuits, ensure the cap seats squarely and engages the gasket evenly to preserve performance. In harsh climate or heavy-duty duty cycles, regular inspection of the gasket surface can prevent leaks before they become a concern. Source One Parts Center provides this part as a dependable replacement for Mack vehicles.