MSW E46 Enhanced Thermostat Housing

The MSW ETH installs just like a stock thermostat housing.

1. Drain the coolant from your system (there is a drain port on the exhaust side of the block).

2. Remove the factory plastic thermostat housing, you will not reuse any parts from it.  Clean the mating surface of any debris of sealant.

3. Install you thermostat w/ o-ring into the MSW ETH.  If your thermostat does not have a small bleed hole in it, we recommend drilling one with a small (~1/16th”) drill bit.  Align this bleed hole so it is at the 12 o’clock position when installed in the engine.

The following steps are for installation not utilizing the included orange silicone gasket.  This method will perfectly seal the thermostat, but just makes clean up upon removal a bit more work.  For installation with the include silicone gasket, proceed to the next (b.) section.

4a. For optimal sealing effect, smear a thin layer of standard black or grey RTV onto the housing perimeter and between the thermostat and outlet portions.

6a. Install the housing to the head, running the three M6 and one M8 bolt in finger tight to ensure the gasket seated properly.  While thread locker is not required, we typically recommend a blue (medium strength) on fasteners used in race cars.

7a. After allowing the RTV to set for around 5 minutes, tighten the M6 bolts to 9Nm (80in-lb) and the M8 bolt to 22Nm (16ft-lb) utilizing a “star” pattern.

For installation with the included silicone gasket:

4b. Use the provide M6 and M8 bolts to align the orange silicone gasket to the thermostat housing.

6b. Install the housing to the head, running the three M6 and one M8 bolt in finger tight to ensure the gasket seated properly.  While thread locker is not required, we typically recommend a blue (medium strength) on fasteners used in race cars.

7b. Tighten the M6 bolts to 9Nm (80in-lb) and the M8 bolt to 22Nm (16ft-lb) utilizing a “star” pattern.

8. Install the 1/8th NPT brass plugs in the sensor ports or your sensors as desired.  These are tapered pipe threads and require a thread sealant or Teflon tape.

9. Install the brass bleed screw into its port.  You can use a long flat-tip screw driver to open/close this bleed screw as needed.  It just needs to be hand-tight and will seal on the rubber o-ring.

10. Install the upper and lower radiator hose onto the barb fittings of the housing, secure with a Norma-style clamp.  The MSW E46 ETH utilizes OE E46 M3 hoses to help eliminate common leak and failure points.

11. Add coolant/water and bleed your system.  The additional bleed screw on our thermostat housing will aid in removing unwanted air from the high point of the head.

12. Crank engine and check for leaks or air in the system.

Note about the electrical connection for the stock thermostat housing:

This plug connector is no longer used and can be secured back on the harness using a zip-tie.  The MSW ETH is designed for motorsports use.  With the stock e-stat removed and a factory tune, you will get a trouble code, though this will not effect running of the engine.  Use of our Test & Diagnostics DME on M54B30 E46 models will disable this feature on the tune and not show a check engine light.