Wallstar oil line bubble,not the usual!

[mikethepipe]

There is a large,10" or more bubble in the clear flexi,if it is bled out completely it reappears in a couple of days or so,rep;laced flexi,remade all joints in the line,filters ok,replaced check valve.
In operation bits of bubble are being sucked in to the burner every now and then,I've watched the line after a series of on/off cycles are performed to try and see which way the air was coming from,tank side or burner side,i.e. pump.
Is there a sure way of knowing where the air is coming from,or is it a case of replacing pump,filters etc until youi find it.
Thanks.

 

[oilhead]

The air will always come in from joints before the pump, but including the joint into the pump. Joints around the non return valve are always favourite for leaks. Did you use new washers with the new valve?

 

[mikethepipe]

Yep. HRM say the pump sealaround the shaft is sometimes a problem.Not like a gas leak where you can detect it with a spray or whatever.Will have to try the pump,just ;like to know rather than guessing.
Thanks for replying oilhead.

 

[oilhead]

If you have a leak before the flexi, it is usually apparent from bubbles coming through with the fuel. Can you hold up the flexi vertical from the non return valve for a while and watch for the bubble to appear? If the air is coming from the pump, it will not pass the high point. If a leaking shaft seal, you should be able to see evidence at the seal. Also, this will only occur when the burner is idle, so you need to bleed the line, and then not run it for an hour or two, or even longer if you cannot see a leak at the shaft. You could also bleed the line and then put a paper trace round the seal while it rests.

 

[mikethepipe]

Thanks oilhead.I'll do those checks. I diod stand and wait watching the clear flexi for a while,both running and idling,not a bubble.I'm thinkling pump.
Cheers.