This is a long running problem. my oil tank is situated outside I have had it checked for cracks/leaks etc and there aren't any. My boiler trips out at least once a week. When I bleed it the oil is contaminated with what I can only describe as a sort of mucus. This usually clears after three or four operations of the pump and then the boiler is fine. Any ideas what this is and what is causing it?

Paul Edmunds, March 2011

its called diesel bug its a microscopic organic life form espesialy prone to live in very low sulphure fuels like road diesel normaly it isent helpwd by the small amount ov water at the botom of ure fuel tank /also as ure fuel level drops air is drawn in this condenses as water and runs down the tank called TANK SWEATING . when the weathe warms up drain the tank totaly and preferbly steam it out at least flush it out thouroly then alough to dry out VERY compleatly , to prevent sweating keep the fuel level as full as posible -no moiste air = no sweating. think about adding a in line filter/seporator - try e bay. look for diesel filter. good luck.

lee jcb mecanic, March 2011