I have a kerosene tank, above ground, outside that fuels the boiler for the house. I keep getting an air lock in the inlet lines that starves the boiler and it consequently shuts down. The technicians (2) that have been called have removed the air bubbles and the system works fine - for awhile. In other words they attend the symptoms but not the underlying problem - the cause of the air bubbles in the inlet line. I can now bleed the air bubble off myself but would like to know what is causing the air to get in the line and to build up (in the line where it loops around into the boiler) so I don't wake up in the morning to find we have no heat or hot water.

Jon Kenyon, April 2009

So I've just tried a simple approach to this problem.

I watched an air bubble get drawn into the fuel line from the boiler unit itself, after it had stopped a burst of heating. The next time it would try to fire up, it would get this air bubble drawn straight in and cause lockout.
Looking in the manual, I saw that the fuel line is meant to rise up past the desired height, and then descend a couple of inches to the valve. Mine didn't ....... so I got a shoelace and tied it up so now the highest point is an inch to the left of the filter; this is where the obligatory air bubble will now rest. The boiler can now receive a better flow of oil when it fires up again, and it seems to be working, at least better than before.

Nilotic, September 2010

i dont know enough about your system but a leak in the suction line will allow air to enter the system and still not leak fuel out. a vacume test would confirm this. is it a lift application? what kind of fuel pump? what kind of burner and type of furnace?

P, April 2009

You don't say what make of boiler you have, or if the oil tank is below or above the boiler, if the oil filters have been cleaned or repalced, I suspect that your boiler is above the tank, in which case you need to look at the flexible oil hoses at the burner, as if even slightly cracked, thesy will not leak oil, but will allow air to be sucked in, as the system is under a vacuum, other causes poor connections on oil line above height of oil or faulty non-return valve at oil tank, or if boiler is HRM Wallstar, faulty Fire Valve (it's special with built in NRV)

Boiler Repairman - Ipswich, April 2009