IT SOUNDS LIKE EITHER A BLOCKAGE OR A FAULT WITH THE PRESSURE LEVEL SWITCH. THIS TELLS THE MACHINE THE AMOUNT OF WATER IN THE DRUM.IF THE END OF THE HOSE CONNECTING THE SWITCH TO THE DRUM BLOCKS WITH UNDESOLVED POWDER OR A FORIEGN OBJECT,THE MACHINE CAN'T SENSE HOW MUCH OR HOW LITTLE WATER IS IN IT.IT WILL KEEP PUMPING.A FAULTY SWITCH MAYCAUSE THE SAME SYMPTOMS.
KEITH(THE SPIN DOCTOR), January 2005