BDFHYK Coolant Expansion Reservoir for GM Trucks & SUVs — OE-fit Polypropylene, Replaces 603-102

The BDFHYK Engine Coolant Expansion Reservoir is a direct-replacement overflow tank engineered to restore proper coolant containment and level visibility for compatible GM trucks and SUVs.

This replacement coolant expansion tank fits a range of GM vehicles and replaces OE numbers such as 603-102, 15075118, 15203949 and others, providing a durable polypropylene construction and clear level sight for routine maintenance. Designed as a like-for-like part, it helps you monitor antifreeze levels without removing the radiator cap and reconnects existing hoses and sensors for a straightforward installation.

Which vehicles does this reservoir work with?

This tank is manufactured to match fit for many General Motors full-size trucks and SUVs. Confirm compatibility by checking your vehicle year, model, and the OE number listed on your original part before ordering.

• Compatible: 2002–2006 Chevrolet Avalanche, Tahoe, Silverado, Suburban (1500/2500/3500 HD Classic)
• Compatible: 2003–2006 Cadillac Escalade ESV/EXT and 2003–2009 Hummer H2
• Compatible: 1999–2007 GMC Yukon XL, Sierra (1500/2500/3500 HD Classic)
• Replaces OE numbers: 603-102, 15075118, 15203949, 15778386, 15778387, 15808715, 15808716, 19353731

How is the build quality and material useful for my cooling system?

The reservoir is molded from high-quality polypropylene (PP) chosen for chemical resistance and thermal endurance. That material helps resist warping, cracking, and the degrading effects of antifreeze over time.

• PP construction reduces risk of leaks and long-term brittleness
• Transparent sections enable quick visual level checks without radiator cap removal
• OE-grade fitment preserves mounting points, hose connections, and sensor locations
• Manufactured to meet performance expectations of original equipment

What should I expect during installation?

Installation is intended to be a direct swap using your vehicle’s existing hoses and fittings. The package includes basic instructions to guide hand-tools-level replacement and restore system integrity.

• Remove the old tank, transfer any reusable fittings, attach hoses and fasteners
• Ensure proper sensor and cap connections if applicable to your model
• Refill coolant to recommended levels and inspect for leaks after warm-up
• Typical installation time: roughly 30–90 minutes depending on vehicle and experience

Why choose a BDFHYK replacement tank over a used or generic part?

BDFHYK supplies a new, OE-standard-quality reservoir made on a production line with inspection controls. A fresh tank eliminates uncertainty from age-related damage that can compromise cooling system performance.

• Brand-new unit avoids hidden cracks, clogged passages, or warped mounting locations
• OE-equivalent dimensions and port locations simplify fitment and reduce modification need
• Packaged with installation guidance to reduce guesswork during replacement
• Customer support available for questions and issue resolution within 48 hours

Who is this for: The BDFHYK coolant expansion reservoir is intended for owners and mechanics maintaining older GM full-size trucks and SUVs that need a reliable, ready-to-install overflow tank. It’s suited to DIYers who want a clear visible coolant level, professional shops replacing worn or leaking reservoirs, and anyone replacing a failed OE part with a cost-effective, OE-equivalent unit. Before purchase, verify your vehicle’s model year and OE number to ensure correct fitment.