International 5900/9900i/ProStar Coolant Reservoir Tank w/ Cap (2003–2020) – Replaces 603-5105
Warranty Information
ROADWEST stands behind the parts we sell. Unless otherwise stated on the product page, your purchase is covered by a 1-Year Limited Warranty against manufacturing defects under normal use.
What’s covered
- Defects in materials or workmanship
- Premature failure caused by factory-related issues
What’s not covered
- Normal wear and tear, cosmetic aging, corrosion from environment/road salt
- Damage from improper installation, incorrect wiring, modifications, misuse, or accidents
- Labor costs (installation/removal), downtime, towing, or other indirect costs
How to file a claim
Contact us with:
- Order number
- Product name / SKU
- Clear photos or a short video showing the issue
If approved, ROADWEST will provide an appropriate resolution (replacement parts, replacement unit, or refund/credit).
Please do not send items back without return authorization.
For more details, see our Shipping Policy, Easy Return & Refund Policy, and Warranty pages.
Shipping & Returns
Most ROADWEST orders ship from our U.S. warehouses within 1–2 business days. Standard ground delivery in the contiguous United States is typically 1–3 business days, with freight service used for oversized or extra-heavy parts.
- Shipping area: United States only (no PO Boxes or international addresses).
- Processing time: In-stock items usually ship within 1–2 business days, Mon–Fri.
- Delivery: Standard ground or LTL freight depending on size and weight.
- Returns: Most unused items may be returned within 30 days of delivery, subject to inspection and our return guidelines.
- Costs: Original and return shipping are generally the customer’s responsibility, unless the issue is caused by ROADWEST (wrong item, damaged on arrival, etc.).
For full details, please review our Shipping Policy and Easy Return & Refund Policy before placing your order.
Keep your International truck running at the right temperature with the High Soar 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
| Brand | High Soar |
|---|---|
| Product Type | Engine Coolant Reservoir / Expansion Tank |
| Compatible Vehicles | International 5900 (2003–2009), International 9900i (2003–2018), International ProStar (2007–2020) |
| OEM Part Numbers | 603-5105, 2591620C91, 3599401F91, 3599401F92, 3599401F93, 3599401F94, 3599401F95 |
| Material | Plastic |
| Exterior Finish | Bare |
| Capacity | 5.8 Liters (approx.) |
| Included Components | Coolant Reservoir Tank + Cap |
| Function | Stores expanding coolant, stabilizes cooling system pressure and helps prevent engine overheating |
| Vehicle Service Type | Heavy-duty semi-trucks – International 5900, 9900i, ProStar |
| Fit Type | Direct replacement, vehicle-specific |
| Recommended Use | Replacement for cracked, leaking or discolored OEM coolant reservoirs |
| Installation | Professional installation recommended for best performance and safety |