I've been lazy replacing the paper filters on my Hakko 808... now it wouldn't suck anymore, very weak suction even though I've put in a new filter, made sure no holes are clogged, etc.
I've resigned myself to buying a new one again (I really need this tool). But first, I decided to take a crack at opening the pump assembly to see what was wrong.
Found the problem, the gasket had been coated with hardened flux and the holes partially blocked also with hardened flux. Soaked the gasket in alcohol and cleaned all pump parts (except rubber) with alcohol and a rag. Put everything back together and turned it on. I could tell it sounds differently now. I could actually hear air being sucked in.
Then tried to suck up solder and it works just like brand new again.
Clean parts #1, 2 and 3. Repeat twice, there's two of them.