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Discussion Starter · #1 · (Edited)
Hey guys,

We've started this project! Check out the details on our blog or posted within this thread! Please feel free to chime in with comments, questions, and recommendations.

http://engineering.mishimoto.com/category/bmw-e46-3-series-coolant-expansion-tank-1999-2006/

E46 3-Series Aluminum Expansion Tank, Part 1: Stock Tank Evaluation

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 out the details noted on the shot below.


E46 Expansion tank ports

This certainly will not be an easy project, considering that the interior of this unit is probably just as complex. Only one way to find out!


Stock E46 3-series coolant expansion tank


Stock E46 3-series coolant expansion tank


Stock E46 3-series coolant expansion tank

To properly replicate the stock expansion tank, we would need to incorporate the internal passages and components. Check out a few shots of this!


Stock E46 3-series coolant expansion tank, internal passages


Stock E46 3-series coolant expansion tank, internal passages

We would also need to address the expansion tank cap, which is key for regulating pressure. We would be designing our tank to utilize the stock cap or a cap of our own.


Stock E46 3-series expansion tank cap


Stock E46 3-series expansion tank cap

The E46 tank also features a sensor mounted in the base, which monitors coolant level. This unit fits into the smaller connection point on the base of the tank.


Stock E46 3-series expansion tank, level sensor

Data Collection

With this unit fully inspected, we grabbed another OEM replacement unit and set to work gathering dimensions using our coordinate measuring machine (CMM) table.


E46 expansion tank on CMM table


E46 expansion tank on CMM table


E46 expansion tank on CMM table

Once we had our dimensions, it was time to sit down with a cup of coffee and knock out the 3D model for this piece using our Solidworks program. Check back next time for a look at our 3D renderings!

Thanks

-John
 

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God bless you, Mishimoto
 

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Thanks for looking into this. I hope you guys make a great tank with precision fittings that fit the factory hoses 100% perfectly. Some may be interested in this! Personally I am set to replace my factory Genuine BMW expansion tank every 60-75k miles. And I will be fine. Did mine 55,000 miles and 5 years ago. Canyon driving, track, commute... all great so far!
 

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My question would be, does this tank need to be so complex internally? Is there a reason for it?

I would be keen to see this product on the market.

Part of the reason is that the tank needs to be able to withstand about 28psi. So there's internal bracing. Also, I'm sure the engineers determined how the coolant needs to flow internally to maintain proper engine temps. Unfortunately, the bean counters took the specs and determined how to make € off replacement tanks.
 

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<a href="http://imgur.com/uZ8hKZa"><img src="http://i.imgur.com/uZ8hKZa.gif" title="source: imgur.com" /></a>


I'm
<a href="http://imgur.com/QHSFtKs"><img src="http://i.imgur.com/QHSFtKs.gif" title="source: imgur.com" /></a>​
 

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Discussion Starter · #15 ·
God bless you, Mishimoto
Haha thank you very much David!

Thanks for looking into this. I hope you guys make a great tank with precision fittings that fit the factory hoses 100% perfectly. Some may be interested in this! Personally I am set to replace my factory Genuine BMW expansion tank every 60-75k miles. And I will be fine. Did mine 55,000 miles and 5 years ago. Canyon driving, track, commute... all great so far!
Thanks Mango! That is our plan exactly. We are working on modeling our aluminum tank and it will include CNC-machined fitting to function with all the stock connections.

Will the cap be cheaper than the G.A.S one?
Pricing is not yet determined, we are still in the early stages of development. I imagine we will have a ballpark figure within the next 4-6 weeks regarding the pricing.

Sub'd. Look forward to following your progress. Best of luck! :thumbup:
Thank you!

This is long overdue. Bravo Mishimoto.
Many thanks!

:thumbsup: Hell yea
Thanks Jake!

My question would be, does this tank need to be so complex internally? Is there a reason for it?

I would be keen to see this product on the market.
Part of the reason is that the tank needs to be able to withstand about 28psi. So there's internal bracing. Also, I'm sure the engineers determined how the coolant needs to flow internally to maintain proper engine temps. Unfortunately, the bean counters took the specs and determined how to make € off replacement tanks.
It sure does. Many of the internal passages separate different chambers of the tank. The design also provides resistance to fluid sloshing about during cornering. If BMW engineers found it necessary to design this piece in such a complex manner, I assume it was done for a reason. As always, we will be testing this unit to ensure it performs exactly like the stock tank.

Would it also be possible maybe to mold on some fins for additional cooling? :) Just throwing it up there. Can't wait for it to be done so I can get it for my next coolant flush.
Interesting idea, although I am not sure how much of an impact this would make, if any. Thanks for the recommendation I will pass it along to the engineering team.

Sign me up for one.
Thanks!

Subscribed! :thumbsup:
Mishimoto ftw!
Thanks for following our progress. :thumbsup:

<a href="http://imgur.com/uZ8hKZa"><img src="http://i.imgur.com/uZ8hKZa.gif" title="source: imgur.com" /></a>


I'm
<a href="http://imgur.com/QHSFtKs"><img src="http://i.imgur.com/QHSFtKs.gif" title="source: imgur.com" /></a>​
Haha fantastic! Thanks buddy. :thumbsup:
 

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Thumbs up, some of use have 2 or more BMW's with this cracking prone part!
 
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