Hissing noise from Boiler.

Recently I have heard an intermittent hissing/whirling noise coming from both the downstairs boiler and the upstairs pump/hot water system. The pump is very hot to the touch. It happens for a couple of minutes when the boiler fires up, stops, then happens again. Please could you help. It is very worrying.



It is an Apollo Boiler and a Grunsfog Selectric Pump.

What type of boiler etc ?

is your system pressurized or tank fed
have you got any automatic air vents in the Airing cupboard

Sounds like the pump is jammed and the boiler is overheating.

This is very common at this time of year - pumps have been asleep all summer and tend to get stuck. They're water-lubricated so corrosion tends to build up around the impeller and shaft.

If you feel up to it, switch off the whole system and undo the large screw in the centre of the pump (with something underneath to catch the drips and use a smallish screwdriver to turn the end of the pump shaft inside. If it won't turn, cheapest solution may be a new pump. If it does turn stiffly, turn it back and forth a few times to loosen it. Put the screw back in and try the system again. If it turns easily, check for other problems: next favourite would be too little water in the system. With everything off, open the air vent on the highest radiator. If nothing comes out, that's your problem.

Er, chaps, the inquiry is 14 months old. And Apollos have overheat stats don't they?