Pesky leak

[740iS]

Had the exact same situation on my 2013 X5 and yes, it WAS the expansion tank! Leaked like that for weeks as I was searching. It doesn't fail in the same way as in an E38, E39 or even E53 where it is catastrophic within a few days.

[E39LV]

AHA! Yeah this leak is definitely playing hide and go seek. Brutal weather coming. Taking it to my mechanic after this weather. It shows up sporadically. Governed probably by the way I drive. I wish it failed like my e39 does. Until you guys shared this, that what was changing my paradigm. Funny how cold weather totally fudges with our rides! %$#*&!

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[andrewwynn]

Cold hurts my joints why not the car's also

[E39LV]

So since I haven't done this expansion tank before, from you that have, is there anything else I should replace "while I'm in there" type of preventative maintenance thing...?

TIA!

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[Maruzo]

I'm also seeing a small coolant leak forming under the front driver side of the vehicle. I am going to use radiator dye to find the source.

[isarkisov]

I had expansion tank replaced on my 09 E70 3.0 about 2 months ago. It wasn’t a super slow leak, but it did leak only while driving though. I also had vent pipe replaced because I broke it while replacing the tank. That hose was really brittle though and I’m happy I had it replaced. When I took the old tank out I couldn’t see any cracks, so still not sure where it was leaking from, but the new tank did solve the problem.

[E39LV]

Thanks for this. No way it was the vent hose though right?

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[Big Smoke]

Originally Posted by E39LV

So since I haven't done this expansion tank before, from you that have, is there anything else I should replace "while I'm in there" type of preventative maintenance thing...?

TIA!

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If your doing an expansion tank? Some come with a new cap included. Some don’t. But make sure you replace both the cap and tank.
As above, not a difficult job. Worst part for me was getting that hose clip off the bottom of the tank. Once off, it was a quick job. Not worth the 12oo the dealership wanted.

[E39LV]

You just reminded me of something I thought was strange when you mentioned the cap. The cap loosens itself... I put a little bit of antifree in [its a miniscule amount] and occasionally when I return to refill, the cap is loose! I make sure to tighten it "clicks" and it loosens by itself! Is this indicative of a specific problem OR do these caps go "bad?" Hell, maybe I should start with a new oem cap...

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[13brian]

Well, I am not an expert on this particular problem per se but, with that new information- if if were me I would certainly try a new cap. Especially since you are not overheating or losing large amounts at once and not preparing for a long trip that could render this catastrophic.