Check for drainage problems
Before you start checking for malfunctioning washer parts when your washing machine refuses to drain, first check the outflow hose from the machine. If it's twisted or kinked, straightening it out may solve the problem. Clogs or kinks in any other drain hoses or pipes lower than the washing machine tub may also be the cause of the drain. Removing clogs might get your water flowing normally again.
Check the washer drain pump
If you hear a humming noise when the washer tub is filled with water, the drainage problem may be the result of a broken drain pump. It's the drain pump's job to remove water from the tub, but it can get clogged by debris or fail for a number of other reasons, including broken belts or impeller blades and seized bearings.
Replace the water-level pressure switch
The water-level pressure switch is responsible for detecting the water level in your washer's tub. If it's defective, the tub may not fill appropriately, drain correctly or could even overflow. If you have a problem with the water-level pressure switch, you need to replace it.