Dorman Pressurized Coolant Reservoir for Ram 2500/3500/4500/5500 (2013–2018) with Cap — Direct-Fit, Heat-Resistant

The Dorman 603-839 is a direct-fit pressurized engine coolant reservoir with cap designed to replace the factory overflow tank on compatible Ram 2500, 3500, 4500, and 5500 models from 2013–2018.

Built for longevity under-the-hood, this replacement coolant reservoir is manufactured from automotive-grade materials to tolerate heat, road vibration, and everyday wear. It’s engineered to match the original part’s mounting points, hose connections, and pressure-handling characteristics so installation is straightforward and performance is consistent with the vehicle’s cooling system design. Always verify fitment by entering your exact trim and model year into the vehicle garage tool before purchase.

How does the Dorman 603-839 restore my cooling system’s performance?

Replacing a cracked or leaking reservoir prevents coolant loss, helps maintain correct coolant levels, and preserves system pressure for efficient heat transfer. The reservoir replicates the original part’s capacity and connections so the cooling circuit can operate as intended.

• Exact-fit design for matching hose and mount locations
• Pressurized cap included to maintain proper system pressure
• Robust material resists cracking from heat and vibration

What should I expect during installation?

Installation is intended to be simple for anyone comfortable with basic underhood work. The tank is built to align with factory mounting points and hose fittings, minimizing modification or fabrication.

• Direct replacement—matches original mounting points
• Hose connections align with factory lines for quick hookup
• Minimal tools required; basic hand tools are usually sufficient

Will this part fit my Ram truck and how do I confirm it?

This Dorman reservoir is compatible with Ram 2500, 3500, 4500, and 5500 model years 2013–2018, but variations in trim and equipment can affect fit. Use the site’s garage tool or enter your vehicle’s exact make, model, year, and trim to confirm correct fitment before ordering.

• Lists compatibility with Ram 2500/3500/4500/5500 (2013–2018)
• Check vehicle trim and equipment in the garage tool for exact match
• Contact customer support for help if you’re unsure about fit

What are the materials and durability features of this reservoir?

The tank is made from durable polymers selected to resist high underhood temperatures, chemical exposure, and constant vibration. Dorman’s aftermarket design follows the original part’s form and function to ensure reliable, long-term operation.

• High-temperature-resistant plastic construction
• Engineered to withstand vibration and road stress
• Designed and tested to mirror factory performance characteristics

Who is this for: The Dorman 603-839 reservoir is intended for owners and technicians who need a dependable, OEM-compatible replacement for a failing or damaged coolant overflow tank on Ram 2500, 3500, 4500, or 5500 trucks from 2013 through 2018. It’s a practical choice for DIY mechanics seeking a straightforward direct-fit repair, fleet managers maintaining uptime, and professional shops replacing worn cooling components without modifying vehicle systems. Confirm vehicle fitment with the garage tool, then install to restore proper coolant containment and system pressure.