BMW B48 Thermostat Retrofit & Heat Management Module (HMM) Delete Kit

Simplify the cooling system on your standalone-managed BMW B48 with the STROM Motorsports B48 Thermostat Retrofit & Heat Management Module Delete Kit.

Designed specifically for BMW B48D engines running standalone engine management, this kit replaces the complex factory Heat Management Module (HMM) with a CNC-machined adapter plate, allowing a more conventional standalone thermostat to be incorporated into the cooling system.

Compatible with engines originally equipped with BMW Heat Management Module P/N 11538642560, this retrofit is an ideal solution for B48 engine swaps, race cars, track builds and motorsport applications using standalone ECUs such as the MoTeC M122.

Replace the Factory B48 Heat Management Module

The factory BMW B48 cooling system uses a sophisticated Heat Management Module rather than a conventional thermostat.

The original HMM incorporates electronically controlled valves and requires communication with the factory engine-management system. This can create additional complexity when installing a B48 into another chassis or operating the engine with a standalone ECU.

The STROM retrofit plate allows the factory HMM to be removed and replaced with a more conventional thermostat arrangement that can be integrated into a custom cooling system.

Designed for Standalone B48 Engine Management

This thermostat conversion is intended specifically for B48 engines using standalone engine management.

Important: This kit cannot be used with a B48 engine running the factory BMW engine management system.

CNC-Machined Thermostat Retrofit Plate

At the heart of the conversion is a purpose-designed CNC-machined thermostat retrofit plate, engineered to replace the original B48 Heat Management Module.

The kit provides the required mounting hardware and genuine BMW sealing gaskets for installation.

Thermostat Options

The retrofit plate can be used with different standalone thermostat configurations depending on your cooling-system requirements.

STROM has tested the following BMW thermostat options:

BMW N52 Thermostat – P/N 11537549476

This thermostat features an additional outlet that can be used when retaining the vehicle's HVAC heater system.

The thermostat mechanically opens at approximately 108°C but can otherwise be controlled through a compatible standalone engine-management system.

BMW N20 Thermostat – P/N 11538635689

This version has one fewer outlet and is particularly suited to race cars without a cabin heater system.

This provides a cleaner cooling-system configuration for dedicated motorsport applications where HVAC functionality is not required.

Kit Includes

• CNC thermostat retrofit plate

• Installation hardware

• Genuine BMW gasket 11539468022

• Genuine BMW gasket 11539468021

Thermostat is not included unless otherwise specified.

Important Compatibility Information

This thermostat retrofit kit is strictly intended for engines running standalone engine management.

It cannot be used with the factory BMW B48 ECU / engine-management system.

The factory Heat Management Module uses electronically controlled valves, including a ball valve operated by two H-Bridge outputs with position feedback through a SENT signal. The factory system also incorporates an additional valve used during cold starts to control coolant circulation.

Because these functions are integrated into the original BMW engine-management strategy, removing the HMM requires an appropriate standalone ECU and correctly configured cooling-system control.

Installation Instructions