@outofmemory This is a closed loop AIO cooler. MSI themselves have issued a recall on this product, it is NOT user error.

Where did the sediment come from? Did you use distilled or filtered water? Was the sediment from internal debris due to manufacturing? You've not provided enough information for fix suggestions beyond - replace the pump. Pump is likely just a diaphram style - flat rubber pushed in and out pushing fluid through small holes with rubber check valves - disassemble and asses the wear and tear and/or clean up all the debris. The pump 'fails' (one manner) if there isn't a differential pressure able to be produced so the pump just flutters without pushing liquid out and allowing return liquid in. With all the small orifices and rubber to plastic interfaces debris or sediment could quickly allow fluid to pass where it shouldn't and a thorough cleaning may be sufficient. Refill with DISTILLED WATER (which shouldn't have any sediment in it).