DIAGNOSIS That loud, sputtering gurgle is normal—it's the signal that the brew cycle is finished. It means most of the water in the lower chamber has been forced up through the coffee and what's left is boiling and pushing steam.
FIX To minimize the drama, you can manually end the cycle a bit early. 1) As soon as you see the coffee stream from the center spout turn from a rich, steady flow to a lighter, bubbly trickle, that's your cue. 2) Flip the power switch on the base to 'O' (off). 3) The residual heat will finish pushing the last bit of coffee through without the violent boiling and sputtering. This also helps prevent over-extraction, which makes coffee bitter.
IF THAT DIDN'T WORK If the sputtering is exceptionally violent or starts extremely early in the cycle (like within a minute), you might have too little water in the bottom chamber. Double-check your water level is up to the safety valve.
HEADS UP Don't let it sit and "cook" on the base after the sputtering starts. Unplug it and, if you're not serving immediately, pour the coffee out of the top chamber into a carafe or your cup. Leaving it sitting on the hot plate will burn the coffee.