BMW 3-Series E46 Expansion Tank 1999-2006

Another update on our E46 expansion tank project! Last time we showed off some images of our prototype unit, noting the numerous precise features we built into our design. This time we are installing the tank in our test vehicle to confirm fitment with the stock shroud and all coolant connection points. In addition, we will check out clearance between the tank and the belt-drive system to ensure appropriate fitment.

Removing the Stock BMW E46 Expansion Tank

Stock BMW E46 expansion tank installed

First we need to remove the stock tank from our test vehicle. As you can see in the image above, the stock fan shroud is the first component to come out before we tackle the expansion tank, hose connections, and mounting plate.

Stock BMW E46 expansion tank installed

After Dan managed to spill coolant all over the garage floor (thanks, Dan!), the stock tank and mounting plate were removed from the E46.

Stock E46 expansion tank removed from vehicle

Separating the tank from the mounting plate can be

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 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

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

Quick project update! As noted in our last post, we had finished collecting data points and dimensional information for the stock tank and were setting our sights on creating a tank of our own.

After pulling our engineers out from under shop vehicles, we set them behind the computer to get this project moving. Check out some of our initial 3D models!

Mishimoto expansion tank, 3D model

Mishimoto expansion tank, 3D model

Mishimoto expansion tank, 3D model

Mishimoto expansion tank, 3D model

Mishimoto expansion tank, 3D model

And here's a shot showing our fill-neck design and upper hose connection!

Mishimoto expansion tank, 3D model

Below is a shot showing the quick-connect fittings located on the base of the expansion tank. As noted in our first post, these attach to the plastic plate on the radiator fan shroud. One of the ports will be capped on manual models.

Mishimoto expansion tank, 3D model

Our tank is being designed to function with all stock connection points and will not require any

Enthusiast groups' feedback plays a massive role in our product development process. Not only is it a great way to bounce ideas off our potential customers, but it also allows us to see exactly what our customers want and need for their vehicles. This project is no different. Due to a substantial amount of demand via forums and social media, we decided it was time to get the ball rolling on this coolant expansion project.

Stock Expansion Tank

In typical BMW fashion, this tank was quite unique and featured some very interesting components, both internally and externally. First, a look at the exterior of the tank. Many of you are very familiar with this, based on the rate of failure reported for this plastic tank.

Stock E46 3-series coolant expansion tank

Stock E46 3-series coolant expansion tank

Stock E46 3-series coolant expansion tank

Stock E46 3-series coolant expansion tank

So, there are five - yes, five - unique fittings located on this tank, excluding the fill-neck connection. Check