BMW E39 failed radiator & failed expansion tank pictorial autopsy, new questions aske
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11-30-2010, 05:35 AM
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Mein Auto: 02 BMW 525i M54 automatic
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Originally Posted by
BMW should comp you a donor car just to drive around and do post mortems on their engineering flaws.
By way of post mortem, below are some pictures which show exactly the weak point in the coolant level visual indicator stick.
Many say it 'disintegrates' but it's pretty tough material. Everything inside the expansion tank is tough material. I doubt anything disintegrates.
I think the weak point is where the stick attaches to the float. You can see in these pictures that it snapped clean off exactly at the top of the float.
In hind sight, I recommend folks be very gentle when they pour fluids into the expansion tank when the bobber stick is up so as not to tilt it. Notice the float itself doesn't have much (any?) side-to-side degrees of freedom.
This picture above is re-used from a previous thread
So, if you tilt the bobber stick, but if the float can't correspondingly tilt (because it's confined to a vertical track), then it seems to me that will break the bobber stick off at the weak connection point - which is exactly on top of the float.
One other thing to note is there are different styles of bobber sticks. I wonder if we can characterize them to tell whether an expansion tank has been replaced in lieu of date codes?
Of course, I use a rather obvious "date code" method when I replace parts:
Last edited by bluebee; 11-30-2010 at
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