Good evening
I have a Dyson DC40. While in use, I'm told that it made a 'popping noise' and the note of the motor changed. After searching around the web I've done the following - washed and dried the filters, cleaned out all the pipes and head unit, dismantled and cleaned the cyclone unit. This has resulted in some improvement to the motor noise but suction is extremely weak - it sounds like the motor is not experiencing much load. I've read about a bleed valve which is responsible for symptoms like this and see replacement ones for sale but I've been unable to work out where on the machine this might be.
Any advice gratefully received.