Glow Worm boiler system banging in pipes.

[GeeN]

I have a Glow Worm Fuelsaver MkII boiler (about 20 years old) that had started producing a lot of banging in the pipes when the central heating and hot water timer started today.

What appears to be happening is that the boiler is coming on full then the water isn't going anywhere and the water is boiling and expanding and then the boiler shuts off for a couple of minutes and the cycle repeats.

I checked the 2 water tanks in the loft. Both are full and the ball cock mechanism is working OK. I did notice that the smaller tank had brown water in it and it was warm. I assume this is overflow when the water in the boiler overheats.

There are 2 single zone valves that appear to be working (I can hear them open and close) and the pump appears to be OK. The pipes from the pump are all hot and I can hear what sounds like the pump running listening to it with a long screwdriver against my ear. I can also hear the pump start and stop when the CH is turned on and off. I have removed the center screw from the pump and lots of water pours out. I then isolated the pump and removed the screw and I can freely turn the impeller.

I have bled all the radiators and found almost no air in them. Also the main system bleeder had only a little bit of air in it.

My thinking is that I will change the pump anyway because it must be about 10 years old.

Is it possible that there is a blockage or an air bubble in the system?
Should I drain the system down and if so are there any procedures to fill it up correctly?

Any pointers or help would be so much appreciated.

 

[gasmick2]

Hi there are several causes that make these low content boilers bang most times it is the pump,, but if there is a blockage then the pump may be cavitating meaning its just circulating in its own bubbles , i had a pump once that was running but the impeller had broken off,, 2 engineers failed to diagnose the problem,, if i were you i would change the pump use the same power pump as is installed i would think that will cure it

 

[GeeN]

Hi there are several causes that make these low content boilers bang most times it is the pump,, but if there is a blockage then the pump may be cavitating meaning its just circulating in its own bubbles , i had a pump once that was running but the impeller had broken off,, 2 engineers failed to diagnose the problem,, if i were you i would change the pump use the same power pump as is installed i would think that will cure it

Thanks for the reply.

I checked the pump and I could turn it and it seemed to be running. However, I changed the pump anyway and this has certainly cured the problem.

I can only assume that the old pump was not pushing enough or any water around the system. The old pump was a pig to remove. I needed 2 more trips to my local Wickes and B&Q for tools and extra pump compression fittings. Had to saw off the seized pump fitting nuts. 5 hours later the job was done. What fun.