Drive belt on washing machine won't stay on - keeps coming off

Sometimes the drive belt comes off. If it does, examine it for excessive freying or wear. If it has several track grooves in it check they are clear and not worn down badly or covered in rubber. The belt might need replacing (buy new washing machine drive belt) but occasionally the belt looks fine and you can wind it back on, which gets it up and running again with no further incidents.

How tight should the drive belt be on a washing machine?

If the belt comes off again

If there's another problem then the belt will come off again, usually straight away or even whilst you are trying to wind it on). For the belt to stay on it must run true. The two parts it runs on are the shaft of the motor and the drum pulley. If either is out of line the belt will just wind striaght off.

The first thing to check ..

.. is the most likely cause, which is the drum pulley. The pullley should not be able to be moved, it should be bolted firmly to the drum spider. If the drum pulley bolt has worked loose the pulley can move forward and backwards and will not run true. Sometimes the pulley itself can be worn where it fits over the drum spider so that even with a sufficiently tightened pulley bolt it won't be held in place. Other times the drum pulley bolt can seem tight but is has actually worked back enough to not hold the pulley in place. The drum pulley bolt may seem tight if it has a loctite 

Do not overtighten this bolt because if it shears off you are in trouble and unless you can remnove it with special tapping tools or other methods you might need to buy a complete new drum or even entire tub as some manufacturers only make sealed tubs.

Other possible causes of drive belt coming off

• The motor could be loose, or even have one of it's bolts come off altogether
• The motor could have one of the arms on its casing cracked or broken causing the motor to not be fixed securely to the tub
• The drum bearings could have worn, or one even collapsed, so that you can lift the drum up and down from the front near the door seal. If there is excessive up and down play there it will allow the drum pulley to wobble and not run true, which you should be able to observe with one person checking the pulley at the back as the other lifts the drum. We aren't looking for minute movement, only obvious movement . (You would expect excessive noise on spin though if this was the case)