ASTAMOTOR Front Engine Coolant Reservoir — Direct-Fit Replacement for Kenworth & Peterbilt, Heat-Resistant Plastic

The ASTAMOTOR 603-5403 front engine coolant reservoir is a direct-fit replacement expansion tank engineered to restore proper coolant recovery and pressure balance for compatible Kenworth and Peterbilt models.

This replacement coolant recovery tank is molded from durable automotive-grade plastic and matches OEM mounting points and hose connections for a straightforward swap. It replaces part numbers 603-5403, 6035403, N5346001, and T1673008, and fits a wide range of Kenworth (T600, T660, T800, W900) and Peterbilt (348, 365, 367, 377, 382, 384, 385, 386, 388, 389) model years listed in the fitment table. The design helps the cooling system compensate for thermal expansion, capture overflow, and return coolant as the system cools—reducing air introduction and helping maintain stable engine temperatures when installed correctly.

How does this reservoir ensure a dependable coolant recovery system?

The reservoir stores overflow coolant when the engine warms and returns it as the system cools, preserving coolant volume and reducing cavitation. Its reinforced plastic resists deformation from heat cycles so the tank keeps its shape and mounting integrity over time.

• Direct replacement for OEM hose and bracket locations—no modifications required.
• Durable, heat-resistant plastic formulation that resists cracking and bulging.
• Properly sized to match original capacity for accurate coolant balance.

Will this part fit my Kenworth or Peterbilt truck?

This ASTAMOTOR tank is matched to the listed model years and replaces the specified part numbers, but always verify fit by comparing mounting points and hose inlet/outlet locations. The tank is intended for the Kenworth T600 (2008–2015), T660 (2008–2017), T800 (2008–2017), W900 (2008–2017) and the Peterbilt models and years shown in the fitment list.

• Replaces 603-5403, 6035403, N5346001, T1673008 for direct compatibility.
• Confirm mounting bracket position and hose diameters before purchase.
• Compatible with the factory coolant cap and sensors where applicable.

How difficult is installation and what tools will I need?

Installation is a straightforward replacement task for most technicians and competent do-it-yourselfers. The unit uses the factory mounting points and hose connections, so removal of the old tank and reattachment of hoses and fasteners is typically all that’s required.

• Basic hand tools: sockets or wrenches for mounting bolts, pliers for hose clamps.
• Allow time to drain or catch residual coolant and refill the system after fitment.
• Bleed the cooling system per vehicle procedure to remove air pockets.

What are the construction and performance features of this tank?

The reservoir is injection-molded from robust plastic engineered to withstand repeated thermal cycling and resist stress cracking. Its finish and connection points mirror the original component to maintain system integrity and reduce the risk of leaks when installed correctly.

• High-quality plastic resists expansion and cracking under temperature changes.
• OEM-style inlet/outlet placements for reliable hose fitment and sealing.
• Built to match original capacity and support system pressure equilibrium.

Who is this for? If you operate or maintain Kenworth or Peterbilt heavy-duty trucks listed in the fitment details and need a reliable, OEM-compatible coolant expansion tank, the ASTAMOTOR 603-5403 is designed for fleet mechanics, owner-operators, and repair shops seeking a durable direct replacement. It is suitable for anyone replacing a damaged, leaking, or aged reservoir and wanting a hassle-free installation that restores coolant recovery function without custom modifications.