Help! My Dyson DC04 keeps overheating and cutting out!?

My Dyson DC04 (silver/green) keeps overheating and cutting out. I have removed the top filter and rinsed but am unsure as to whether I can remove the hepa filter on the bottom (near motor) and wash this filter as it isn't mentioned at all in the user manual.
Any suggestions will be greatly received!
Thanks in advance.