I have the Asus ROG Strix Z390-E Gaming, and just installed an EKWB loop for CPU and GPU cooling. I connected the pump (EK-XRES 140 SPC PWM Classic RGB) to W_PUMP+ connector (G on the diagram in the manual on page 1-17). On CHA_FAN2 (F on the diagram), I have a Y connector for the fans attached to the radiator. Also, in order to get past the CPU fan error, I plugged a fan into CPU_FAN (connector B).
I power on the machine, and quickly try to get into bios, before the machine freezes up. Watching the pump & CPU LEDs, it seems to cycle on and off every 5 seconds. So what I am guessing is the CPU isn’t getting cooled, and is freezing up. There are no error lights on the mobo.
I have tried disconnecting power to GPU, and just using on board video (both HDMI and DP), but no luck. It is actually worse and the screen turns to pixelation and then seems to multiply that pixelation, until it ultimately freezes.
There have been 2 times it "booted", but first gave me Stop Code: DRIVER_IRQL_NOT_LESS_OR_EQUAL and the other was PAGE_FAULT_IN_NONPAGED_AREA
but it might be a good idea to post wich water cooler you have i also think it should cool recardless of bios settings bios setting just help to do its job better i myself have a asus z390-h and a kraken watercooler (forgot wich model but it was the biggest a year ago)
I posted which pump I am using, but it has seemed to work itself out. I pulled one stick of ram, and things booted up. Put the ram back in and all things seem fine. The turning off and on was aurora was configured for breathing.