I had this broken KÜHLER H2O 620 closed loop water cooler that just didn't cool anymore. You could hear that there was air in the pump but it didn't seem to be leaking so I thought I could just take it apart, refill it and hopefully it would work again.

So I cut the tubes

And I started draining the radiator and..

What the hell is that mucus in there??

It smells worse than it looks.. either the chemicals they added to the coolant dissolved some kind of rubber in the radiator or something has gone wrong in the production. I'm going to refill it with distilled water later..

I also cleaned the pump/heat sink

This is when I realized that my tubes (which are actually aquarium tubes) were too large for the sockets so I had to keep some of the original tubes

And put the new tubes over the old ones

And seal them with zipties

I did the same with the other end of the tubes (the ones that go in the pump)

And connected everything

The fun starts -> the filling

The radiator is taking a bath in distilled water after flushing out the rest of the mucus with normal water. Those freaking water bubbles never seem to go away.. after flushing for a few minutes there were still bubbles.

Still bubbles..

After playing around for some time I was able to get the big bubbles out and only small ones near the output of the pump remained.. but I don't think that'll be a big problem.