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Old 02-19-2013, 09:51 AM
avoisin avoisin is offline
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Location: Oregon
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Mein Auto: 2004 X3 2.5i
Persistant cooling leak from expansion tank

I've been plagued in the last few weeks with a coolant leak that just refuses to go away. I recently had to change out the heating/cooling thermostat underneath the expansion tank, and now I can't stop a leak from that area.

Best I can tell, the leak is coming from the two holes at the bottom of the expansion tank, where they sit on the mount. One has a pin clip to hold it in place, the other just sits by friction. It's the latter that seems to be wedging just a bit loose, and causing a slow, small drip. The part is the "Cooling Water Connector" that I just cannot get to stay flush after assembly. You can see it here on the great DIY:

DIY Cooling Replace, post #14, picture #5. It just wiggles around too much in the housing, there's probably a good 1/8" of play at least.

I've tried simply reseating, adding some silicone putty, but nothing I can think of will get that connector to sit flush consistently. Only other thing that comes to mind is a real adhesive or something to truly bond that connector/mount area to the tank, but I really don't want to resort to that.

Anyone have ideas??
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Old 02-19-2013, 07:44 PM
Supercourse Supercourse is offline
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Location: British Columbia, Canada
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Mein Auto: 2004 X3 2.5i
Originally Posted by avoisin View Post

Anyone have ideas??
Have you checked the o-rings inside those 2 ports?

I don't think removal of the tank to replace the A/T thermostat should be enough to flatten them out, but you never know.

It's usually tanks and thermostats get replaced one time together, so the o-rings are possibly not designed to be re-used.

Maybe carefully extract the problematic one, soak it in some coolant mix to make it more pliable, and reseat it?

Other than that, maybe there is a hairline fracture at the bottom of that one port.
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Old 02-22-2013, 04:16 PM
avoisin avoisin is offline
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Location: Oregon
Join Date: Feb 2013
Posts: 11
Mein Auto: 2004 X3 2.5i
Update - I ended up using some metal tape to add a bit of width to that pipe. That was enough to get the friction fit to work again. It took some effort to get things back together, but a hammer made things work ok. I did it by wrapping the slide-out part with 2 layers of high temp metal tape, putting the tank back on, then hitting the top of the tank with a rubber mallet (and the bottom, somewhat) until things came together. Best I can tell, the slow drip has stopped.

I could probably have also gotten a new expansion tank and the lower slide-out piece, but this solution wasn't half bad. And now I have extra metal tape!

The o-ring is kind of embedded into the tank, and I figured I'd just leave it alone and try the metal tank. I didn't really see an easy way to wedge it out like you were suggesting. I think the problem came from me just mucking around down there and damaging the o-rings in the first place, since I am pretty new to all this.
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