MITZONE Aluminium Thermostat Assembly with Housing for BMW E46/E39/E60 — Direct-Fit, Includes Thermostat & Gasket

MITZONE's upgraded aluminum thermostat assembly with housing is a complete replacement unit that fits many BMW models and replaces part number 11537509227.

This all-in-one kit combines a metal thermostat housing, a calibrated thermostat, and a gasket to restore coolant control on compatible BMW engines. Built with an aluminum housing for improved longevity over factory plastic pieces, the assembly is designed as a direct-fit replacement for a wide list of BMW chassis and model years. It’s helpful for routine maintenance or when diagnosing coolant leaks and overheating caused by worn plastic housings or failed thermostats.

Which BMW models does this thermostat assembly fit?

The MITZONE assembly is manufactured to match the original mounting points and coolant passages on many BMWs produced around the late 1990s through mid-2000s. Check exact engine and year compatibility before ordering to ensure correct fitment.

• Fits E46: 323i (1999–2000), 323Ci (2000), 325Ci/325i/325xi/330Ci/330i/330xi (2001–2006 for various models).
• Fits E39/E60 series including 525i and 530i (1999–2005 model years where applicable).
• Fits SUVs and roadsters like X3 (2004–2006), X5 (2001–2006), Z3 (1999–2002), Z4 (2003–2005).
• Replaces BMW OEM part number 11537509227 for compatible applications.

How is this MITZONE unit different from the original thermostat housing?

MITZONE uses an aluminum housing instead of the common factory plastic, which reduces the chance of cracks under heat cycling and extends service life. The package delivers a ready-to-install assembly so you don’t need to transfer components from the old unit.

• Aluminum housing resists warping and heat-related failure better than plastic.
• Includes thermostat and gasket for a full, single-item repair.
• Prepared for direct bolt-on installation with OEM-style mounting points.

What should I expect during installation and maintenance?

Installation typically involves draining part of the cooling system, removing the old housing, swapping the assembly, and refilling coolant. Basic mechanical skills and common tools are usually sufficient; torque to manufacturer specs and test for leaks after cycling the engine.

• Requires coolant drain to below the housing level to prevent spillage.
• Inspect hoses and clamps while replacing the housing for preventive maintenance.
• Bleed the cooling system per vehicle procedure to remove air pockets.

Will this part solve coolant leaks or overheating?

Replacing a damaged housing and a worn thermostat often remedies leaks and incorrect thermostat operation that can cause overheating. However, diagnose the entire cooling system—hoses, water pump, radiator, and sensors—if problems persist.

• Fixes leaks originating at the housing flange and mating surfaces when installed correctly.
• Restores thermostat opening temperature if the original unit was sticking or failed.
• If overheating continues, further system diagnostics are recommended.

Who this is for: Drivers and independent mechanics who maintain BMW models from the late 1990s through the mid-2000s and need a durable, single-piece replacement for the thermostat and housing. This kit is suited for owners replacing cracked plastic housings, addressing leaks at the thermostat cover, or completing a preventive cooling-system service with a metal upgrade.