I hope you've been using distilled water and bleeding the system when you add these 8 cups of water. If you don't bleed the system, sure it may have fluid in it, but the waterpump is just splashing around and not pushing the water everywhere it needs to go if there are air bubbles present in the system.

There are 3 different motors/fans that circulate coolant through the system. 1st being the 3 stage aux fan, which usually runs when the A/C is on, sitting in traffic on hot days, etc.

2nd is the mechanical fan attached to the motor which contains a waxy like substance. It shouldn't spin freely (hence why it sounds like an airplane taking off till like 3k rpms) unless it's failed completely due to the stuff leaking out. Some seize, which is really bad (sounds like an airplane all the time) and can damage the hood, radiator, hoses etc from the centrifugal force of the fan blades breaking off and destroying everything in their path (i've seen pics, not pretty).

3rd is the little motor that feeds the heater diverter valve, which controls the drivers/passenger side heater. There isn't really a way to tell it's failed unless you pull it from the car and test it in your hands.

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