Causes of grease, slime and black mould inside washing machines
Washing machines now commonly suffer from a build up of a greasy deposit and bacteria which causes bad smells, rots hoses & door seals and blocks the pressure system causing overfilling or spin failure. An even more serious consequence of this problem is that the aluminium based drum spiders can be corroded by the build up of grease and gunge, which can cause one or more of the drum’s arms to break. This is often fatal to the washing machine.
This problem was virtually unheard of before the 1980s but when detergents started to become more environmentally "friendly" and liquid detergents were invented this issue suddenly appeared. It seems that the problem is worse when a combination of factors are involved, but almost everyone suffering the worst cases of this slimy grease uses 40 degrees washes almost exclusively. This, combined with poor quality detergents, not using the recommended quantities, or only using colour-friendly detergents which contain no bleach (allowing bacteria to thrive) can seriously rot a washing machine inside.
Here’s an example of the level of gunge that can build up inside a washing machine.
Large deposits of grease, slime and undissolved detergent have built up on the underside of this door seal, which can cause smells. If you were to wash greasy plates in a plastic washing up bowl with the water at 40 degrees you would expect the plates to come clean but when emptying the bowl there is likely to be a greasy film coating it. To break down grease you need higher temperatures. Washing the same plates at 60 degrees or higher I would expect the grease to be dissolved more effectively.
To check if your washing machine is being badly affected, carefully examine the inside of the door seal for slime and grease. Pull the lip back in front of the drum and look underneath and on the lip of the tub. If the door seal is covered in black mould it will probably need replacing.
Smells from the plumbing
Washing machine smells can also be caused by plumbing issues. Check out this article for more details – Smells caused by plumbing faults.
Get rid of stubborn washing machine smells
Try the advice here – getting rid of Washing machine smells