Bimmerfest - BMW Forums - View Single Post - BMW E39 failed radiator & failed expansion tank pictorial autopsy, new questions aske
View Single Post
Old 12-02-2010, 07:44 AM
bluebee's Avatar
bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
I found another failure mode for the expansion tank!

I can see the failure; but I do not know the implication.

It's a mystery to me, that can be resolved if someone helps us understand how this other half of the expansion tank actually works.

Please help explain what this does!

In this picture, you can see the thin incomplete bulkhead which hides the second failure point in my expansion tank.

Notice, behind the bulkhead, is an apparently MOVING part, which seems (perhaps) to slide up and down the incomplete stalk through a rather large hole in the apparatus' corner.

Mine was fixed in place, locked down, by the stalk being in the center and not at the hole. But what is the hole for, if not for the stalk.

And, why would this 'box' slide if it wasn't meant to slide, fitting perfectly in the inside contour of the expansion tank???

Also notice this chamber is fed by the auxiliary water pump ... which may hint at its purpose.

But, the main question, is what is the purpose of this chamber?

And, did it fail?

Notice, for example, the stalk is blocking upward motion of this box.

I think we'd need a third expansion tank autopsy to confirm or deny my hypothesis that this chamber failed in my expansion tank because the stalk moved out of the corner hole and blocked upward motion.

Please, the next person to replace their expansion tank, please cut it open and take care to note the position of the stalk and box in the hidden chamber behind the thin incomplete bulkhead.

Do YOU have an idea about what this chamber is for and how it might work?
Attached Thumbnails
Click image for larger version

Name:	bulkhead_1.JPG
Views:	24515
Size:	49.9 KB
ID:	256846   Click image for larger version

Name:	bulkhead_2.JPG
Views:	108881
Size:	78.7 KB
ID:	256847   Click image for larger version

Name:	bulkhead_3.jpg
Views:	28321
Size:	63.2 KB
ID:	256848   Click image for larger version

Name:	bulkhead_4.JPG
Views:	24450
Size:	56.7 KB
ID:	256849  
Reply With Quote