Frequently Asked Questions About Peterbilt 389 Coolant Reservoirs

What years of Peterbilt 389 do these coolant reservoirs fit?

Our coolant reservoirs are designed to fit Peterbilt 389 models from 2008 to present. However, there are slight variations between pre-2014 and post-2014 models due to mounting bracket changes. Always verify your truck's VIN and model year when ordering, as some custom configurations may require specific reservoir styles. If you're unsure about compatibility, our team can help verify fitment with your VIN number.

What's the difference between plastic and aluminum coolant reservoirs?

Plastic reservoirs are OEM-style replacements that offer cost-effectiveness and adequate performance for standard applications. They typically last 5-7 years under normal conditions. Aluminum reservoirs provide superior durability, better heat dissipation, and won't crack from temperature cycling like plastic can. While aluminum costs more upfront, many drivers prefer them for heavy-duty applications or extreme climates. Both options maintain proper coolant levels, but aluminum reservoirs often feature sight gauges and drain plugs for easier maintenance.

How difficult is it to install a coolant reservoir on my 389?

Installation typically takes 30-45 minutes and requires basic hand tools including wrenches, pliers, and a drain pan. The process involves draining coolant, removing 2-3 mounting bolts, disconnecting the overflow hose and sensor connections (if equipped), then reversing the process with the new reservoir. The main challenge is accessing the lower mounting bolt on some models. Having a flex-head ratchet helps considerably. Always ensure proper coolant bleeding after installation to prevent air pockets.

Do these reservoirs come with caps and sensors?

Most replacement reservoirs include a new pressure cap rated at 15-16 PSI, which is standard for Peterbilt 389 cooling systems. However, coolant level sensors are typically sold separately as they vary by truck configuration. Some trucks use float-style sensors while others use electronic sensors. Check your original reservoir to identify which sensor type you need. We recommend replacing the cap with every reservoir change to maintain proper system pressure.

What capacity coolant reservoir do I need for my 389?

Standard Peterbilt 389 models use either a 1.5-gallon or 2-gallon coolant reservoir, depending on engine size and configuration. Trucks with ISX15 or X15 engines typically require the larger 2-gallon capacity, while smaller engines may use the 1.5-gallon size. The physical dimensions are similar, but using the correct capacity ensures proper coolant expansion room and prevents overflow issues. Your existing reservoir should have the capacity marked on it, or you can verify with your engine model number.