SYKRSS Engine Coolant Reservoir Tank 603-5403 for Kenworth & Peterbilt — Polypropylene Direct-Fit

SYKRSS 603-5403 is a direct-fit engine coolant expansion reservoir designed to replace OE N5346001 / T1673008 on selected Kenworth and Peterbilt models.

This replacement coolant reservoir is engineered from heat-resistant polypropylene to handle heavy-duty truck cooling cycles while restoring proper coolant overflow and recovery function. It’s built to the original equipment shape and mounting points so installation is straightforward for technicians and owners who service W900, T800, T660, T600 and a range of Peterbilt heavy-duty models. The tank lets you monitor antifreeze level without removing the radiator cap and returns excess fluid to the system as the engine cools.

Which trucks does this SYKRSS coolant tank fit?

The SYKRSS 603-5403 reservoir covers a broad set of late-model Kenworth and Peterbilt trucks. Fitment matches multiple model years for W900, T800, T660, T600 and many Peterbilt variants including 377, 385, 386, 382, 365/367/384 and 389.

• Compatible OE references: N5346001 and T1673008 (service cross-reference).
• Fits Kenworth: W900 (2008–2018), T800 (2008–2018), T660 (2008–2017), T600 (2008–2015).
• Fits Peterbilt: 377/385 (2008–2014), 388 (2008–2015), 386 (2008–2016), 382 (2008–2017), 365/367/384 (2008–2018), 389 (2008–2019), 348 (2010–2018).
• Always confirm fit using vehicle filters or parts diagrams before purchase.

How does this reservoir handle heat, vibration and coolant exposure?

The tank is molded from high-grade polypropylene designed for long-term resistance to hot coolant and the vibrations common in heavy trucks. Its material retains shape and sealing performance under cyclic thermal stress to help prevent leaks and maintain system pressure balance.

• PP plastic resists heat and chemical exposure from engine antifreeze blends.
• Reinforced mounting points mirror OE fit to reduce movement and stress.
• Translucent body allows visible level checks without opening the radiator cap.

What practical benefits will I notice after installing this replacement tank?

Replacing a cracked or faded overflow tank restores correct coolant recovery and preserves cooling-system efficiency. You’ll regain a clear sight of coolant level, reduce risk of contamination, and avoid unnecessary coolant loss that can lead to overheating situations.

• Restores overflow storage for expanded hot coolant and recovery during cooldown.
• Helps prevent oil dilution and unnecessary wear by maintaining proper coolant volumes.
• Improves diagnostics—quick visual checks of antifreeze level without tools.

What should I expect during installation and warranty support?

The 603-5403 is intended as a direct replacement so installation is often a simple removal-and-replace job using existing hoses and mounting brackets. SYKRSS includes a 12-month warranty and responsive support for fitment or quality questions.

• Designed for bolt-on replacement using existing hardware when compatible.
• Check hose routing and clamp condition; replace clamps if corroded.
• SYKRSS warranty covers manufacturing defects for 12 months; contact support for assistance.

Who is this for: Fleet mechanics, owner-operators, and maintenance teams working on Kenworth and Peterbilt heavy trucks who need a reliable OE-form coolant expansion tank. It’s suited to anyone replacing a cracked, discolored, or leaking reservoir who wants OE-alike fit, visible coolant level checks, and a durable polypropylene construction backed by a one-year parts warranty.