[lowrydr310]

I discovered a minor coolant leak from the joint where one of the lines from the transmission oil heat exchanger attaches to the radiator. This is a plastic piece with an o-ring that slides into the radiator and is secured with a torx screw.

I changed the o-ring last time I replaced the radiator two years ago with a genuine BMW part but it still never fully sealed. Just recently I had the cooling system drained and decided to replace this with a larger o-ring which worked. I even pressure tested the entire system afterward to confirm there were no leaks. But I guess when things are nice and hot it's not the same. I'm still smelling coolant from the same area and I suspect it's one of the quick connect fittings for the transmission oil heat exchanger.

I can't get a good look without removing the intercooler, but I do remember last time I had it out and was reinstalling the radiator fan, there were some drips of coolant on one of the connectors. When the radiator fan is removed this heat exchanger is left dangling with nothing to support it but the lines. Definitely not ideal for 20 year old o-rings.