Sometimes the drive belt comes off. If it does, examine it for excessive fraying or wear. If it’s a belt with 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?
Fairly tight. You should be able to pluck the belt and get a nice resounding "ping". The belt shouldn't be over tightened though. Roughly speaking there should be some sideways play, you should be able to move the belt from side to side roughly a quarter of an inch. Many belts are now fitted with non adjustable belt. So when a belt stretches you have to buy a new one. Crafty eh? If a belt is adjustable there should be one motor bolt that is fitted on a slot instead of a fixed hole.
That way the position where the bolt is tightened can be adjusted along the slot. Most washing machine motors these days are just bolted to the tub with small holes and no slot available to adjust the belt tension.
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 straight off.
The most common cause of belt coming off
A loose drum pulley is the most common cause. The pulley should not be able to be moved, apart from obviously round and round as it turns the drum. It should be bolted firmly to the drum spider with no play in it. 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 tightly enough and will wobble. You can a buy drum pulley (with a Price-match guarantee).
Warning: Do not over tighten the drum pulley bolt because if it shears off you are in trouble, and unless you can remove 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..
More causes of drive belt coming off (if it looks in good condition)
- 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. It’s rare but even hairline cracks can do it.
- Conversely, a motor bracket on the outer drum itself could be broken causing the motor to be not fixed securely to the tub and moving during spin – see the section headed “Broken motor bracket” here – Repair a plastic outer drum
- 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)
- Maybe the belt isn’t damaged, but has stretched enough to be quite loose on the pulley and is slipping off
How to fit a new belt
Fitting a drive belt onto the drum pulley should be very easy, it’s just a matter of placing the belt under the motor pulley and winding it slowly over the drum pulley until it winds all the way on. Some washing machines however do not have a back panel that can be removed. This makes it much more difficult. If there is no back panel to take off, or there is just a pathetic little inspection panel, you will have to try and fit the belt from the top.
Ensure the washer is disconnected from the mains and remove the lid. Try to hook the belt onto the motor pulley and then feed the belt onto the drum pulley whilst slowly turning it.
You may find this very difficult to do without the belt constantly coming off. In difficult cases I used to use a cable tie to hold the belt onto the pulley to act as a third hand. Obviously don’t forget to remove it after if you do.
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