Have had one of these, probably been running for 4-5 years now, just tonight it was making a hell of a racket, could hear it thru the whole house. 
 
Its a 40 or 50L/min one (from memory) 
 
Any pointers on what may have gone wrong with it? I got it off trademe ages back so any record of who it came from is long gone,  
 
Says COM-3540 on it on half a sticker that is left on it. 
 
So anyway, need to sort it out, or replace it. Any issues with opening these up? I have never had any luck fitting new rubber bits to the crappy little pumps and having them last, but I am assuming that something larger like this would be easier.