Radiator tank leaking

[tye1138]

Ok, this is really odd.

I've got a 1991 525i Touring with a relatively new radiator...

I go to take off the filling tank on the radiator because it was full of sludge at the bottom and I wanted to clean it. I NEVER had any problems with the tank previous to this and I was very careful at taking it apart.

After re-assemble, the edge of the bottom of the tank right where it seals into the radiator seems to be leaking. Its not leaking a WHOLE LOT, but it will leak out the contents of the tank within a hour or two. I pulled it out, checked the seals, checked the o rings, they all looked perfectly fine.

BUT: There are 2 grooves for o rings on the seal from the tank to the radiator. The BOTTOM o ring is there, the top groove never had an o ring present.

Maybe its bad o rings? Anybody ever hear of this issue?

I'm technical saavy, already replaced the entire cooling system due to the previous owner loosing a metal piece in the radiator that ended up ruining everything in the dam system!

This little issue is givin' me greif!

[rps1072]

I believe the expansion tank only has a lower 77mm and an upper 14.5mm o-ring. You might just try getting new ones and see if that stops the leak. It's a checp place to start. Check for a leak further up on the tank--it might be leaking and pooling around that lower seal.

[Kakaire]

While on this, were you able to identify which colors attach to the Coolant level sensor connect? Mine wasn't connectecd and hence was getting this time to time warning gong about my collant level. I see a hanging socket, yellow in color, though the way its shaped doesn't seem to be the one that connects any ideas?