BMW E46 3 Series improved expansion tank - Cooling System Maintenance

[danewilson77]

Per Turner Motor Sports:

BEHR has updated the expansion tank version to have better quality (~2 years ago). They simply thickened the plastic walls to help prevent cracking.

These expansion tanks last much longer.

This should be a key bit of knowledge when shopping around for a rebuild kit or individual tank.

Thanks to Keith (kayger12) for digging up the email and confirmation on this.


Part numbers we have (from Turner)

Part #: 17117573781 This is the most recent expansion tank design from Hella-Behr, the OEM supplier to BMW. It replaces the original BMW part number 17137787039.

Sent from my S4 > Mason, OH

[kayger12]

Now I just wish there was an easy way to determine who has the new vs the old. Lots of reports on line of people getting well over 100k miles out of the OE tank.

I also found a good number of low mileage failures with respect to non-OEM tanks.

[danewilson77]

Was looking to see if these kits had the Behr:

http://www.ecstuning.com/BMW-E46-330i-M54_3.0L/Engine/Cooling/Refresh_Kit/ES2063861/

Didn't say. Even the write up says you'll need to do this rebuild every 80k miles.

Sent from my S4 > Mason, OH

[kayger12]

Can you shoot one of your contacts at ECS an email and see if they can clarify?

[330i ZHP]

good info

[JupiterBMW]

So as per the info in Dane's post, can we assume that the kit sold by Turner would include this better quality expansion tank? I'm feeling like I should do a huge maintenance hit and the cooling system is on my radar.

[quikryptonite]

I'm about ready to do the cooling system refresh. Good to know, thanks Dane.

[Avetiso]

Great info. 72k on my OE tank, and it looks perfect. But it'll be time to go soon enough.

[iZHP]

Just did the cooling system on the 325i...it had an OEM Expansion tank...still had the barcode sticker on it. The entire side cracked from top to bottom. The OEM replacement seemed identical...

[BavarianZHP]

Interesting. I wonder how much thicker it actually is. From an engineering standpoint, it would mean that there were some significant changes to the dimensions of the tank. It would have to be bigger overall (maybe someone can measure it?). Now, if they kept the dimensions the same (which would be odd), the volume capacity would be forced to shrink with the thicker walls... Meaning that the max coolant level bobber would have to be adjusted a bit... Complicating the situation a bit more.

[BavarianZHP]

So assuming they actually thickened the walls, one could first measure exterior differences from the two. Then if they were identical, attempt to measure their volumetric capacity to see if there's a difference (which I would hope not since this would affect the coolant level). Now, if both were identical metrically, one could still justify the increase in longevity of one vs another if one was made with a different material (but with same dimensions, which would be my hope - better plastic, not just simply thickening it).

[kayger12]

I'm wondering if they didn't improve the stiffening ribs on the inside as well. Dug up this old post on BFc when I was researching. Unfortunately, the pic links are dead.


I wondered about this, particularly after my second OEM tank failed in 12 months. So after I replaced it yet again, I decided to do a failure analysis on the failed tank, and was shocked at how bad a few of the mistakes were that lead to failure.

So here is the tank. I had already cut the top off and cut out the side port, so this is just to show the whole tank:



Next, looking down into the tank from the top. Note that I have removed a bunch of internal parts already, but one can quickly see that the side that bulges out is not supported to the center for most of the length. Not good.



To make things more clear, I then cut off one corner of the tank to expose the central rib that goes down the middle of the side which bulges out.



Now that the inside of that portion of the tank is exposed, the problem is remarkably clear. The mistakes here are really bad. They clearly blew it on multiple accounts including the decreasing thickness of the stiffening rib and the insufficient cross section of material connecting the side of the tank to the middle. The loading is clearly more than the fiber reinforcement to the plastic can take and it fails in shear (indicated by the 45 degree orientation of the cracks. Then the whole tank self destructs due to excessive deflections. It is not to supprising that these fail all the time.



Clearly if the side of the tank was connected to the middle at some point above the side port, the stresses would be significantly lower. More to the point, if the stiffening rib did not thin out as it does the deflections in the side of the tank would also not contribute to the problem. I also noted that one corner of the tank did not crack (the corner in the lower right corner in picture 2 above). This corner had a much higher radius than all the others. again stress concentrations.

This is very sloppy engineering. It is very much on par with the abismal design work done on the rear subframe mount. In both cases the engineer who did the design work shows a complete lack of comprehension of stress concentrations, how stress is distrubuted in a structure, and the design limits of the materials they are using.

I sincerely hope the new tank (part number 17 11 7 573 781) has structural improvements inside versus this one (part # 17 13 7 787 039)!

[danewilson77]

Part number info added to post #1.

Sent from my S4 > Mason, OH

[WOLFN8TR]

Good info...

I replaced my original exp tank at 118K, not too shabby.

[Washburn]

I know this is an old thread, but I saw several people wondering (also on other threads), which supplier with refresh kits has the exp tank bearing the NEW part number.

I found this kit - it does have the new part number for the exp tank:

http://www.oembimmerparts.com/BMW_Cooling_System_Refresh_Kit_p/e46coolrefrkit.htm

What do you guys think? I know it's not the most complete overhaul kit, but is it good enough to cover the basics for peace of mind? At least one can be certain that it has the new exp. tank...

How does it compare to the ECS Level 1 kit? (not sure if this kit has new exp. tank or not)
http://www.ecstuning.com/BMW-E46-330i-M54_3.0L/Engine/Cooling/Refresh_Kit/ES263518/
EDIT: NOPE - ECS level 1 kit contains a VAICO exp. tank.

[danewilson77]

I think the OEM kit is a good kit Washy.

"No flamesuit required"

[Washburn]

Thanks, Dane. Just wanted an expert opinion. :)
I know that there are mega kits that have so much more, but at that price point, I think it should do.

[danewilson77]

Yeah....the only thing you could add here is the radiator, Trans cooling water hose, some odd ball stuff. I think it's solid.

"No flamesuit required"

[ELCID86]

One sensor is missing and you'd probably want to do the pulleys, tensioners and idlers.
Wonder where the tank is made?


Thumbs, iPhone, Tapatalk.

[Washburn]

Are you referring to the ECS or the other kit?


Sent from my NOT bent iPhone 6 using Tapatalk

[aurelius]

I have purchased loads of non-OE E46 expansion tanks and every single one of them is made in China, including the Behr-Hella. If Behr-Hella is still the OE supplier, then presumably the tank with the BMW sticker on it (the one you'd get from a BMW dealer parts dept.) is also made in China.