International 5900/9900i/ProStar Coolant Reservoir Tank w/ Cap (2003–2020) – Replaces 603-5105

Keep your International truck running at the right temperature with the ROADWEST Engine Coolant Reservoir Tank with Cap. Designed as a direct replacement for multiple OEM numbers, this heavy-duty expansion tank helps maintain proper coolant levels and protect your engine from overheating during long-haul and heavy-load operation.

Engineered for International 5900, 9900i and ProStar trucks, this reservoir tank offers a precise fit and durable construction to withstand constant heat, vibration and pressure changes in the engine bay. It comes complete with a cap, making it an ideal solution when your original tank is cracked, leaking, or discolored.

The reservoir is thoroughly tested to deliver consistent performance under harsh conditions, providing a reliable place for excess coolant to expand and return as temperatures change. Whether you’re replacing a failed unit or performing preventative maintenance, this tank helps restore your truck’s cooling system efficiency.

• Vehicle-specific fit – Compatible with International 5900 (2003–2009), International 9900i (2003–2018) and International ProStar (2007–2020); designed for a direct replacement fit.
• OEM cross-reference – Replaces OEM part numbers 603-5105, 2591620C91, 3599401F91, 3599401F92, 3599401F93, 3599401F94, 3599401F95 for easy identification.
• Durable plastic construction – Manufactured from high-quality plastic to better withstand heat, pressure and engine vibration over long service life.
• Restores cooling performance – Provides a proper expansion space for coolant, helping to stabilize system pressure, reduce leaks and protect the engine from overheating.
• Complete with cap – Includes reservoir cap so you can replace the entire assembly at once and avoid issues from worn or damaged caps.
• Ideal for heavy-duty use – Built for demanding commercial applications where trucks operate under load for long hours and require reliable cooling components.
• Easy replacement – Designed to match the OEM shape and mounting points for a straightforward installation by professional technicians or experienced owners.

Package Includes:

• 1 × Engine Coolant Reservoir Tank
• 1 × Reservoir Cap