Confusing series of issues - Knackered pump the root cause?

[CVP]

All

The symptoms are as follows;

1. Really loud intermittent banging from the boiler (Potterton, but not sure of the exact model). Just after the banging it sounds like there's a rush of air up the hot pipe coming from the boiler, almost as if the boiler is boiling the water in it and it's this hot water shooting up the pipe. Banging every 10-15 mins I'd say

2. Intermittent tapping noises in some radiators (upstairs ones only)

3. Hot radiators upstairs, stone cold downstairs

4. Pump next to hot water tank is humming away like crazy and is very hot to the touch.

5. All rads have been bled and now only water is coming out, no air

I'm a bit of a noivce to this but I'm sure the system is an open system,
ground floor is boiler & 3 rads. First floor is hot water tank, motorised valve, towel rail plus 4 rads and pump. Attic cold water tank plus what I take to be the expansion tank further up in the roof.

We've been in the house 4 years and haven't really done anything about the system, it's always worked perfectly until about a week ago.

Any ideas as to the likely cause?

Cheers

Chris

 

[kevplumb]

if it has one undo the screw in the middle of the pump and see if the shaft is turning

if no screw use a screwdriver and see if you can hear the pump running

it could well be locked

also check the motorised valve is working

 

[CVP]

it could well be locked

also check the motorised valve is working

Thanks kevplumb.

Stupid Q - if it's locked does that mean complete replacement is the easiest thing or could a big air lock lock it?

Re the motorised valve. When I've been looking at this over the last few days and turning the HW and CH on and then off individually it does move, so to a novice like me would appear to be working.

Chris

 

[kevplumb]

if you can get the shaft to turn you might be lucky

would change it soon tho

 

[CVP]

Thanks all. Pump was knackered. Nice and toasty again. Took the opportunity to whack in some descaler and will drain the system down this wekend and add the inhibitor.

Chris