I have a Maytag (FAV6800AWW) top load washer. The cold water won't shut off except at the valve. The cycle will run properly with hot water but if you have the cold on it just runs until it overflows.

Servicing Water Inlet ValvesIf the washer won't fill or fills very slowly, if it overfills, or if the water is the wrong temperature, the water inlet valves could be faulty. These components are easy to locate and very easy to replace, at little cost. When you suspect an inlet valve is faulty, first check to make sure the water faucets are fully turned on and properly connected to the hot and cold inlets of the valves. Then check the screens in the valves; if they're clogged, clean or replace them. If water doesn't enter the tub, set the temperature control to the HOT setting. If there is no water, set the control to the WARM setting. If all that comes out is cold water, the hot-water inlet valve is faulty. Reverse the procedure to test the cold-water valve, setting the control first on COLD and then on WARM. If the tub overfills, unplug the washer. If water still flows into the tub, the valve is stuck open. In any of these cases, the valves should probably be replaced.

There should be markings on the washer near the inlet valve that will have a "H" or "C" for hot or cold. If not, hook the hoses up and run cold water only. If the water comes out hot, you will know that the hoses are crossed. It won't hurt anything to run the machine this way.

The Bleach dispenser valve may have failed.

Are you into to troubleshooting the issue?

If so I will help. Check to see the washer top is not bowed downward at the Console loaction. If the Pic come thru make sure the water channel on the left side of the lid lines up with the left side (bleach) dispenser valve I'll post a pic but lately the picks won't be displayed. This forum is difficult for DIY support.

If the pics don't come thru Google Neptune TL Washer FAV6800AWW post in the Maytag washer part of the forum for support my time is free as an owner.

Turn off the water to the machine. Disconnect the cold water hose from the back of the machine and put it in a large bucket. Turn on the water to see if you get full-pressure cold water from the hose. If not, the shut-off valve or other plumbing has a problem.

If you do get cold water from the hose, check the strainer inside the hose fitting on the back of the washer. Clean it if it is clogged. If you still don't get cold water in the machine, you have a problem with either the solenoid valve or the cold water fill contacts in the timer (the timer won't start until the tub is up to the selected level, but if the valve isn't opening or the supply line is otherwise blocked, the machine will never fill). Sometimes in this case you can hear the solenoid valve humming (normally the sound is masked by the running water).

If the problem is a clogged strainer, clean out the hot water strainer also.

I find I get better wash results with warm water (runs both hot and cold for the wash cycle). The soap is more active than in cold water, so I don't need quite so much, and the machine doesn't take as long to finish a cycle since it fills faster. Of course, the cold water has to be running to get the energy savings compared to hot only.

the hot water inlet valve is shot replace it

two problems here,
your shaft seal is running on its last leg
the sound is unmistakeable and always described the same...
the water issue, you probably have a trickle leak through the cold water valve
the mixing valve is quite an easy repair, but I would have to say with all honesty, it probably time for a new machine
the hub seal is a tub replacment call
2 hrs of labor if hes good
and the tub runs around 500.00 dollars
sory for the bad news

Replace the water fill valve on the washer.

If your machine is a FAV6800AWW or FAV9800AWW the (upside down u and f) may be a “NF” for no fill error. The washer has tried to fill the machine with water and has sensed a water fill issue. The control board has shut the wash cycle down with an “NF” error to the display because of excess time to complete the water fill portion of the wash cycle.
Will the machine complete the cycle with Hot water only or Cold water only? I would do a Quick Wash cycle just to test with an empty wash basket.
Regardless of the above test and assuming you have good water pressure for both Hot and Cold supplies to the washer I would do the following. Close the water source valves to the washer and remove the Hot and Cold hose connections at the back of the machine and check for clogged inlet screens. If the water inlet screens are free of restrictions I would go into Service Mode and turn on the Hot and Cold water valves on one at a time and make sure the tub will fill with about 2 inches of water in about 3 minutes in service mode. Check both Hot and Cold inlet valves individually see page 16 of the SM Board Output Test, enter service mode and do the function test for both Hot and Cold Water Valve’s. If the inlet screens are clean and you have water fill restrictions in service mode we may need to look at replacing the water inlet valve assembly. You can turn on the drain pump in service mode to empty the tub or just start a wash cycle and the machine will empty the tub.
The Service Manual for reference. Sears Parts Direct for reference.

solenid valve
may be faulty.
to test disconect from the cold side and atch to the hot side,
the solenid valve is an electronic valve that switched the water on and off its usally atched inside of the back of the machine where the hose attaches to.

..
http://en.wikipedia.org/wiki/Solenoid_valve

the water level sensor is defective and need to be replaced