LOSTAR Radiator Surge Tank Coolant Reservoir for Silverado & Sierra 2017–2021 — OE Direct Fit, Reinforced Plastic

LOSTAR 603-009 radiator surge tank is a direct-replacement coolant reservoir engineered to fit 2017–2019 Silverado and Sierra 2500HD/3500HD and 2019–2021 Silverado 4500HD/5500HD/6500HD for reliable coolant containment.

If your heavy-duty GM truck needs a dependable overflow/reservoir assembly, this LOSTAR surge tank offers an OE-style swap that matches factory mounting points and hose interfaces. Built from reinforced plastic and supplied with a secure cap, it replaces part numbers such as 84257137, 84214124, 84174037 and related OE codes so you can restore the original coolant routing without custom modifications.

Will this reservoir fit my Silverado or Sierra model?

Yes — the 603-009 surge tank is manufactured to be compatible with specified heavy-duty GM trucks and is intended as a direct replacement for listed OE numbers. Confirm year and model against the fit list before ordering to ensure compatibility.

• Fits 2017–2019 Silverado and Sierra 2500HD/3500HD
• Fits 2019–2021 Silverado 4500HD/5500HD/6500HD
• Replaces OE part numbers: 84257137, 84214124, 84174037, 84138913 and similar
• Designed for direct bolt-on installation without trimming or adapters

How durable is this coolant surge tank and what material is it made from?

The tank is molded from high-strength automotive-grade plastic chosen to tolerate under-hood heat cycles and coolant exposure. Its construction focuses on resistance to cracks, warping and seal failures that commonly affect cheaper reservoirs.

• Reinforced plastic resists heat and chemical breakdown
• Factory-style mounting bosses reduce stress at attachment points
• Pre-installed cap included for an immediate, leak-resistant assembly
• Manufactured to meet common OEM fit and function expectations

What makes this an OE-style direct replacement versus an aftermarket workaround?

LOSTAR engineers the 603-009 to align with original factory dimensions, hose locations and mounting tabs so it replaces the original part with no modification. That means a straightforward swap using existing hoses, clamps and fasteners.

• Precision dimensions match the factory surge tank layout
• Hose fittings and ports located to accept stock lines directly
• Mounting points and brackets mirror OEM geometry
• Designed to work with the vehicle’s original coolant cap and pressure requirements

How will replacing my surge tank help my truck’s cooling system?

Installing a correctly sized and sealed reservoir restores proper coolant expansion and recovery, helping the cooling system maintain correct levels and pressure balance during engine temperature changes. While not a cure-all, a sound surge tank reduces the chance of coolant loss and the related risk of overheating due to low coolant volume.

• Improves coolant containment during thermal cycling
• Helps maintain engine coolant level and system pressure
• Prevents leaks from cracked or deformed old tanks
• Supplied cap ensures a secure seal after installation

Who is this for: This LOSTAR 603-009 reservoir is aimed at owners of compatible Silverado and Sierra heavy-duty trucks who need a dependable, direct-fit replacement for a failed, cracked or leaking coolant surge tank. It’s suited to fleet managers, DIY mechanics and service shops that require an OE-style part to restore proper coolant containment and hose routing without custom fitting.