hello there i had the same thing on my 54 ghia 2ltr tdci along with the air con which had stopped blowing cold 2 weeks later so i took it to kwik fit who pumped up the gas and to get rid of the smell they debugged the system as the bacteria builds up in the pipes.the cost of the debug was £19.99. which has worked they also said that it was not filter.
hopefully this is of help to you
bundiboy