almighty screaming sound in airing cupboard

[Welshdragon]

I have just installed a replacement rad in bathroom. Prior to starting the job I had drained the rads, and turned off the stop cock to the expansion tank in the loft. Before setting up the system again we turned the hot water on. After a couple of hours we heard an almighty screaming noise coming from the airing cupboard, on opening the cupboard door it was clear that the problem was either the cylinder tank or pump. We turned the boiler off and the noise stop immediately, I refilled the radiators. Everything was ok, not too many leaks! The following day we turned the hot water on again and after an hour there was a humming noise from the airing cupboard. This time the noise was definitely coming from the pump with some vibration of the cylinder. If we had left the boiler on for longer this may have turned to a scream. The outside of the pump was boiling! The central heating system was NOT on just hot water.

No other pieces of equipment were touched except the stop cock to the loft expansion tank. Once that was turned on every thing filed up as normal. What have I done?

The pump is from new (1996) WSP Gold.

 

[oilman]

You probably have damaged pump bearings.

 

[ryanj]

Did you turn the electrical supply to the boiler, pump, etc. while you were doing this?

 

[djbunny]

try venting the pump and the pipework above, if this fails its a new pump

 

[croydoncorgi]

Likeliest explanation is air in the pump, so it was running with dry bearings. This is a VERY quick way of wrecking a water-lubricated pump!

If it is the pump making the noise, turn it off NOW.

Then loosen the big screw in the centre of the 'motor end' of the pump (better not to remove it completely). If just water drips out, too late - the bearing is toast. If water and air comes out, let it bleed until its only dripping water. If nothing comes out, you've probably got an air lock so the pump has no water in it at all.

If / when the pump is full of water, turn it back on and see if the noise has stopped. If not - new pump head required.