X4XZ Coolant Reservoir with Sensor for BMW 120i–520i (2012–2019) — Direct-Fit 603-880 OE Replacement, Thermoplastic

X4XZ 603-880 coolant reservoir with sensor is a direct-fit radiator expansion tank designed to replace worn or leaking reservoirs on select 2012–2019 BMW 120i through 520i models.

This replacement surge tank restores a sealed coolant circuit and provides the correct mounting and sensor connections for the listed BMW 2.0L four-cylinder models. Built from sturdy thermoplastic and tested for compatibility, the unit includes the OE-equivalent sensor mounting and cap seat to help maintain proper coolant level monitoring and pressure behavior without modifying your original plumbing.

How will this reservoir affect my engine cooling system?

The reservoir collects expanding coolant from the radiator and returns it as the system cools, preventing air pockets and maintaining level. Using a properly sized, undamaged tank keeps the closed cooling system operating as engineered and helps the coolant sensor report accurate levels to the vehicle electronics.

• Replaces OE# 603-880 and OEM references 17137642158, 17137609469.
• Includes integrated sensor mounting for original wiring compatibility.
• Molded ports match factory hose locations — no cutting or splicing required.
• Resists heat and coolant fluids for long-term service life.

Which BMW models does this reservoir fit and how do I confirm compatibility?

This tank was produced to fit many BMW 2.0L L4 platforms from model years 2012–2019, including various 1, 2, 3, 4 and 5 Series variants. Confirm fit by matching part numbers or comparing mounting points and sensor connector shape with your original tank.

• Fits: 120i (F20), 220i (F22/F23), 228i (F22/F23), 320i/320i xDrive (F30), 328i/328i xDrive/GT (F30/F31/F34), 420i/428i (F32/F33/F36), 520i models listed.
• Cross-check OE numbers 17137642158 and 17137609469 to verify match.
• Inspect hose locations and sensor plug shape before purchase.
• Refer to model and year combinations in the product details list for clarity.

What are the benefits of replacing a damaged reservoir with this unit?

Swapping a cracked or leaking tank stops coolant loss, prevents engine overheating risk due to low level, and restores proper sensor readings. A new, correctly fitted reservoir also reduces the chance of vapor lock and helps preserve thermostat and head gasket longevity by maintaining correct system pressure behavior.

• Seals coolant system to prevent leaks and contamination.
• Restores accurate coolant-level sensing for dashboard warnings.
• Durable construction reduces repeat replacements.
• Direct-fit design minimizes installation time and complexity.

How difficult is installation and what comes in the package?

Installation is straightforward for anyone familiar with simple engine-bay repairs: remove the old tank, swap hoses and sensor connector, and secure the new unit into factory mounting points. Hardware and cap seat are provided as part of the molded assembly; basic hand tools and coolant top-up are all that’s typically required.

• Package contains one complete coolant reservoir (cap included in seat).
• No printed manual included — basic mechanical skill recommended.
• After installation, bleed the cooling system and check for leaks.
• X4XZ provides 24-hour customer support and a 1-year product service period.

Who is this for: This X4XZ 603-880 coolant reservoir is intended for BMW owners, independent mechanics, and repair shops maintaining 2012–2019 BMW 120i, 220i, 228i, 320i/328i, 420i/428i, and 520i models with the 2.0L L4 engines. Choose this part if you need a direct-fit replacement with the correct sensor interface and OEM-equivalent references for a reliable, like-for-like restoration of your vehicle’s cooling circuit.