I have however found out that these fans seem to stall (increasing RPM doesn't increase airflow) when running over 40% PWM, they clearly were designed for free-flow operation, not to be mounted directly on the heat exchanger. One day I might get annoyed enough about this to go crazy and buy a pair of Deltas, since they have 120mm models with PWM and guide vanes (can create more pressure, downside is noise and manufacturing cost), but at the moment I can't justify spending over $80 on 2 fans, no matter how ridiculously overpowered they are...
Middle-ish left - the CPU block.
Middle-ish right - the reservoir/expansion tank. It's made from acrylic sheet (which is probably older then I am) bonded with CA glue. In/out ports are threaded brass, the input one is a flange nut that has been sanded flat, glued with CA to wall (which already had a hole in it) and after the glue set, I secured it with an acrylic plate that had a hexagon cut into it (prevents the nut from exerting shear forces onto the glued surfaces). The output is a threaded stub and a flange nut is holding it in place. So much CA glue was used to make sure it's not going anywhere. The output also has a...thing...on the inside to keep it from picking up air, it looks like a scoop.
The tank is has a baffle in the middle, it's intended purpose is to give bubbles more time to rise to the surface and not be sucked in by the pump. Secondary and unintended effects is a nice wave indicating flow.
Upper right - An Eheim 1048 bought waaaaay back (today I would have gone for a 12V powered pump) in ~2005. While it has nice ceramic bearings - picture a white smooth ceramic shaft that goes into a smooth ceramic tube of matching diameter, almost loose fit (slides freely but no perceptible play) - it's still a synchronous motor and as such, it can (and will!) spin in either way, depending on when (AC phase) you turn it on, which means the impeller has to have straight instead of nicely curved blades and can (deliberately) freely rotate some 60° in relation to the magnet. The end result of these features is not-so-unnoticeable AC hum from the coils and if air bubbles manage to get in the pump, you get horrible rattling and clackety noises, which subside only after the air is expelled out. The pump cannot to this on it's own, so it has to be re-started, usually a couple of times. Once this is done and it's snugly fit in it's foam vibration dampener, the fans (or magnetic HDDs) are louder then the pump.
As you can probably see, I tried my best to avoid galvanic corrosion as much as possible, the only critical place is the pump output fitting, as it's made out of steel, not nickel-plated brass like the nut on pipe is. In case you are wondering why, it's a fitting made for hydraulics, nobody seems to be making a G 1/4 male to G 3/8 male fittings out of brass in this country. I have coated the inside of the fitting with a resin-based lacquer, but I fear this may not be enough.
One other possible place might be the radiator, as it's not clear what it's actually made out of, flanges seem to be brass, but the tubes are supposed to be copper. Also, they are soldered/brazed (more different metals).
We will see how it held up as I will be doing scheduled maintenance in the near future, main reason being I need to add L-fittings to nearly everything in order for it to fit in the case the way I want, not the way the minimum bend radius of the pipes will allow me. Other items to be added is a drain and fill valve, because attempting to fill (or drain) the system without them is a pain in the butt I wish to never have to experience again.