Clanking pipes and steam when boiler turned on

[Rob99999]

Boiler was old but working fine. Then I turned it on and it fired up like normal and seemed okay until the pipes next to it started clanking loudly and steam started to come from what I assume must be some kind of vent in the pipework above the boiler.

Water pressure is fine (1.5 bar according to gauge)
Rads are fully bled
Water pump is full working, although I presume it's not actually pushing water around the system?

So... I guess the problem is that due to some kind of blockage / airlock the water doesn't seem to be moving, hence the steam, hence the clunking. Does that sound correct? And if so, any suggestions for a remedy?

Thanks guys (and gals?)

Untitled

• Rob99999
• 23 Aug 2014
• 1

ps arrow on pic marks where the steam came from

 

[TCCHeating]

Are you sure the pump is working? How did you test it? I suggest you have another look at the pump

 

[Rob99999]

thanks for the reply

Well... I took the gold screw out of the front and a little water came out. The impeller inside spun freely when I turned it with the screwdriver, and when I returned the system back on check, it was spinning around at a million miles an hour like I presume it's supposed to

Presumably that means it is in fact working? Or does it not?

 

[TCCHeating]

Not necessarily, the impellor shaft could be sheared, meaning the motor is spinning but the impellor isn't. Only way to check it is to isolate the pump using the 2 valves and removing the head by unscrewing the allen key bolts.

 

[Rob99999]

Okay cool, so just to check, if I turn the gold valve just above and just below the water pump fully clockwise so that they're off, it's then safe to remove the pump and check to see if it's sheered? Does that sound correct?

Sorry to be simplistic but I want to double check so I don't do something disastrous!

 

[TCCHeating]

Yes thats right. But be careful, most of the time those pump valves don't always turn off fully! Make sure you have a container ready to catch any water before you remove the head.

If you find the pump is ok then you have either a blockage or an air lock which is causing the water not to circulate properly around the system. The steam you are seeing from the auto air vent is because the boiler is overheating and the water is boiling causing the banging sound

 

[Rob99999]

Okay, will give it a go a little later - hoping I don't get too wet!

If the impeller is fine, how would I go about getting rid of a blockage or an air lock?

thanks for your help btw

 

[xr4x4]

Oh.. Nice pump...wilo?

Will prob have a plastic impeller.

I had one the other day, the impeller was just spinning on the shaft, I just used some glue to glue it back on. Fine now.

 

[Agile]

Whilst the impeller can shear off the shaft, its more common for the eye of the pump to become blocked with dirt!

Tony