ASTAMOTOR Front Engine Coolant Expansion Tank 603-5403 for Kenworth/Peterbilt — Direct-Fit, Reinforced Plastic

ASTAMOTOR 603-5403 is a direct-fit front engine coolant expansion reservoir built to replace the original water recovery tank on compatible Kenworth and Peterbilt models.

This replacement coolant reservoir is designed to restore coolant recovery, help maintain proper system pressure, and reduce the risk of coolant loss from the overflow circuit. Molded from reinforced plastic, the tank is shaped and ported to match factory dimensions so it installs quickly and works with the vehicle's existing hoses and fittings. Confirming compatibility with your model year and OEM part numbers ensures a straightforward swap without modification.

Which trucks and part numbers does this reservoir replace?

The ASTAMOTOR 603-5403 reservoir replaces several OEM numbers and fits a range of Kenworth and Peterbilt model years. It was produced to match the original mounting points and connections found on the listed vehicles, helping preserve factory routing of coolant lines.

• Replaces part numbers: 603-5403, 6035403, N5346001, T1673008.
• Kenworth fitment: T600 (2008–2015), T660 (2008–2017), T800 (2008–2017), W900 (2008–2017).
• Peterbilt fitment: 348, 365, 367, 377, 382, 384, 385, 386, 388, 389 (various 2008–2018 years).

How easy is it to install and what should I check before buying?

Installation is intended to be a direct replacement with no special tools required beyond common hand tools. Before purchase, verify the OEM part number on your old tank and confirm the model year range to avoid fitment issues. Inspect hose diameters and mounting bracket locations to ensure compatibility.

• Direct-fit design for original mounting points and hose connections.
• Typical installation time: a few minutes to an hour depending on access and accessories.
• Check OEM number and compare hose ends for a match.

What is the construction like and how does it perform under heat?

The tank is manufactured from high-grade plastic engineered to resist thermal cycling and cracking from engine bay heat. Its material choice helps maintain shape and sealing under pressure changes, while the molded inlet/outlet ports align with factory coolant plumbing. Properly installed, the tank supports coolant recovery and contributes to system pressure balance.

• Durable plastic resists expansion and thermal fatigue.
• Molded ports and mounting bosses mirror factory geometry.
• Designed to assist the cooling system's overflow and refill functions.

What signs indicate my truck needs a new coolant reservoir?

Visible cracks, coolant loss, or inconsistent coolant level readings are common indicators a reservoir should be replaced. Other signs include coolant smell in the engine bay, milky residue from a degraded tank, or coolant leakage under the vehicle after shutdown. Replacing a failing tank prevents loss of coolant and helps keep the cooling circuit functioning as intended.

• Surface cracks, hairline fractures, or bulging walls.
• Coolant puddles beneath the front of the truck or wet mounting area.
• Rapid drops in coolant level without obvious radiator or hose leaks.

Who is this for: This ASTAMOTOR 603-5403 expansion reservoir is aimed at fleet technicians, owner-operators, and repair shops maintaining Kenworth T600/T660/T800/W900 and Peterbilt 300–389 series trucks within the listed model years. It suits anyone seeking a cost-effective, factory-form replacement reservoir to restore proper coolant recovery and system pressure behavior. Always confirm part numbers and vehicle fitment before ordering to ensure a correct match.