Originally Posted by danjo-xx
This is something I'm interesed in learning how to do, are you saying that we should disconnect the feed pipe (and let if flow till clear of air) and then re-connect, if so would air not get into the system while bleeding the line?
Nope, its with out doubt the best way to bleed an air locked oil line, you dont have to undo it fully, just crack it open until loose, move it about to break contact and allow some oil to flow out. Once you have a trickle its enough for the boiler to run, any air that might be still trapped in oil pump etc will pass out through nozzle on first fire.
Its tricky to locate the nut, you have to remove the burner cover, norm just two large flat head screws, then tuck yourself down to see the nut on the formed bend. I keep spanners for each type of hose, 12, 13 and 14, sometimes I've used 16.
Too much confusion happens with different types of oil boilers, a lot of people make a mistake by loosening the wrong nut to bleed oil line, then they mess up oil pressure or air which leaves boiler running incorrectly.
Beside the oil line inlet you might find another nut, its only a blank cap directly beside the burner oil line inlet nut. The space which is blanked by the nut is for installing a tiger loop should your oil tank be lower than boiler, in some cases loosening this nut can also bleed air out of oil line. I was given all these tip's from a great oil boiler service man, passed away since but like it do, thats the only way he removed air from oil line.
I never touch bleed screw, never even bother to look for it, always crack open line going into burner and never one single problem, been doing so for years.
Some times if a oil user runs out of oil regular, constant bleed calls, I fit a small solder tee on oil line with the dead end having a small bleed like you see on a rad, that way user can bleed oil line without touching the burner.
If your not so confidant, before breaking oil line at burner, shut off supply at fire check valve, small brass wheel head should be real close to burner, turn that anti clock wise until its free, it shuts off supply, then crack nut at burner open, turn supply back on until you see oil flowing, shut it off again, tighten nut at burner then open wheel head by tightening down fully.
Air locks stop oil from flowing to burner, thats the problem, not air in burner. Once oil can flow, the burner takes care of the rest.