eliminating sour smell?

Hi I have a hoover quatro washing machine and it has a sour smell which I cannot get cleared,I have stripped and cleaned all the pumps and pipes as well as the drain system to which it is coupled .Short of stripping the drum assembly there is nothing left to clean,also have used bleach and dish washer
agents to no avail can you suggest a remedy (other than a new machine ) Regards Allan Downs.