MM Shroud 4

E46 3-Series Aluminum Expansion Tank, Part 3: First Prototype

Interested in picking up this awesome aluminum coolant expansion tank? Check out our pre-sale details linked below!

Mishimoto E46 3-Series Aluminum Expansion Tank Pre-Sale

Big news for our E46 followers! Our aluminum prototype of the BMW E46 expansion tank is complete. Gone are the days of roadside tows and antifreeze puddles messing up your driveway. Enjoy the images of our awesome prototype below!

First Prototype Images

Mishimoto prototype BMW performance parts
Mishimoto prototype BMW performance parts
Mishimoto prototype E46 expansion tank
Mishimoto prototype E46 expansion tank

We designed five different CNC-machined pieces to attach to this tank. This allows for factory fitment with the variety of quick-disconnect fittings featured on the fan shroud plate and coolant lines.

Mishimoto prototype BMW E46 expansion tank CNC fitting
Mishimoto prototype BMW E46 expansion tank CNC fitting

We went with a subtle logo design with the simple Mishimoto “M” stamped into the front of the tank. Very simple and quite nice looking.

The most complex feature on this tank is the lower CNC-machined quick-connect fittings that attach to the radiator fan shroud plate. The tank was designed to fit with both automatic and manual models.

Check out a few shots of this unique component!

Mishimoto prototype BMW performance parts
Mishimoto prototype BMW performance parts
Mishimoto prototype BMW performance parts
Mishimoto prototype BMW performance parts

And a shot looking up into the tank through these fittings.

Mishimoto prototype E46 expansion tank CNC fitting
Mishimoto prototype E46 expansion tank CNC fitting

The top of the tank also incorporates a few interesting features, including a CNC-machined radiator cap fill neck and an additional hose connection.

The silicone coolant line functions to relieve coolant and air in the event of an over pressurized system, and this line will be attached to the final product. This tank will function exactly as the stock unit does, and we will be including a cap that matches pressure ratings from the stock piece.

Mishimoto prototype E46 expansion tank fill neck and coolant port
Mishimoto prototype E46 expansion tank fill neck and coolant port

Test Fitting

Before test fitting on our vehicle, we first wanted to check fitment on the stock shroud setup. These CNC-machined pieces are complex, and we needed to ensure that everything clicked into place appropriately before bolting our prototype onto our test vehicle.

Mishimoto prototype BMW E46 expansion tank installed on fan shroud
Mishimoto prototype BMW E46 expansion tank installed on fan shroud

Fitment with these lower connection points is perfect and exactly like the OE tank. Success!

Mishimoto prototype BMW E46 expansion tank installed on fan shroud
Mishimoto prototype BMW E46 expansion tank installed on fan shroud
Mishimoto prototype BMW performance parts
Mishimoto prototype BMW performance parts

Fluid Level Sensor

If you’re not familiar with the fluid level sensor on the E46, you may not know how it functions within the tank. I’m not saying it’s over engineered, but perhaps this component is more complex than necessary (especially if you need to design it in an aluminum tank).

The fluid level sensor does not come in contact with the coolant but is housed in an enclosed chamber. Magnets attached to a float in a separate chamber work with the sensor to indicate when the fluid drops below an optimal level. This might sound like a bunch of gibberish, especially for the visual learners, so we created this detailed illustration!

Mishimoto prototype E46 expansion tank level sensor cutaway
Mishimoto prototype E46 expansion tank level sensor cutaway

In the image above, you can see our float assembly within the tank. The red piece is a magnet and float assembly surrounding the cylinder that contains the sensor. As the fluid level changes, the magnet will drop and reach the sensor contacts. The magnet then pulls one of the metal contacts into the other, completing the circuit to activate the low-fluid indicator. Below is another cutaway with labels on each component.

Mishimoto prototype E46 expansion tank level sensor cutaway
Mishimoto prototype E46 expansion tank level sensor cutaway

Definitely something unique for our engineering team to design! Once we have this installed in our test vehicle, we will be able to confirm if any adjustments to the magnet or assembly are necessary.

We then installed the sensor to ensure that our CNC-machined fitting accurately matches the features on the stock sensor. Good news! The stock sensor fits right into place in our prototype.

Next time we will see if the internal components function properly once installed!

Fluid level sensor installed in Mishimoto prototype BMW E46 expansion tank
Fluid level sensor installed in Mishimoto prototype BMW E46 expansion tank

Coming Up!

Soon we will be pulling our test vehicle into the shop to test fit this tank and ensure that all additional coolant lines fit. We will also be checking the functionality of our fluid level sensor system. Check back for more updates on upcoming Mishimoto BMW performance parts!

Thanks for reading!

-John

Interested in picking up this awesome aluminum coolant expansion tank? Check out our pre-sale details linked below!

Mishimoto E46 3-Series Aluminum Expansion Tank Pre-Sale

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