LOSTAR Coolant Overflow Reservoir Tank for 2008–2017 Kenworth & Peterbilt — Heavy-Duty Plastic Direct-Fit (OEM N5346001)

The LOSTAR Heavy Duty Coolant Overflow Reservoir (603-5403) is a direct-fit replacement coolant expansion tank engineered for 2008–2017 Kenworth and Peterbilt trucks with Cummins or CAT engines.

This replacement overflow bottle is made from durable plastic and built to meet strict quality-control standards so you can restore proper coolant recovery and visible fluid monitoring without modifying existing plumbing. It replaces OEM dealer part number N5346001 and is designed to match the fit, mounting points, and hose connections used on many heavy-duty Kenworth and Peterbilt models shipped between 2008 and 2017.

Which truck models and engines will this reservoir fit?

This LOSTAR tank is specified for a broad range of Kenworth and Peterbilt vehicles produced in the stated model years. It fits trucks equipped with Cummins or CAT engines and matches the original mounting configuration for a simple swap.

• Compatible Kenworth and Peterbilt models from 2008–2017, including T660, T680, T800, T880, W900 and multiple W and legacy series.
• Specifically replaces OEM part N5346001 for a direct mount and correct hose alignment.
• Intended only for trucks with Cummins or CAT powerplants—verify engine type before ordering.

How does installation and fitment work for a quick replacement?

Installation is designed to be straightforward for a technician familiar with coolant systems: unclip and drain the old tank, remove the mounting hardware, and transfer hoses and cap to the new unit. The replacement aligns with factory bolt locations and hose fittings to minimize downtime.

• Direct-replacement design, no cutting or drilling required.
• Uses original hose connections and cap thread to maintain system integrity.
• Plastic construction reduces corrosion risk compared with metal alternatives.

What materials and durability features does this reservoir offer?

The tank is injection-molded from heavy-duty plastic formulated to resist heat cycles and automotive coolant exposure. Quality control checks ensure consistent wall thickness and sealing surfaces so the bottle maintains shape and leak-free performance under typical heavy-duty operating conditions.

• Durable plastic body engineered for thermal and chemical resistance.
• Precision-molded cap seat and hose bosses for reliable sealing.
• Manufactured to match OEM dimensions for consistent performance.

What should I check before purchasing to ensure correct replacement?

Confirm your truck’s model year and engine type (Cummins or CAT) and compare the OEM part number on your existing reservoir. Visual matching of mounting points and hose locations will help avoid fitment issues; contact your parts specialist if you see any differences.

• Verify truck make, model, and year (2008–2017 coverage).
• Confirm engine manufacturer (Cummins or CAT) for compatibility.
• Check existing overflow bottle for OEM number N5346001 where available.

Who this is for: The LOSTAR Heavy Duty Coolant Overflow Reservoir (603-5403) is aimed at fleet maintenance technicians, owner-operators, and repair shops that need a reliable, OEM-form-fit replacement for Kenworth and Peterbilt trucks built from 2008 to 2017. If you need a straightforward swap to restore coolant recovery and clear visible level monitoring—without modifying the vehicle—this replacement provides a cost-effective, durable solution that matches the factory layout for trucks running Cummins or CAT engines.