No heating and noisy pumps after refitting a radiator

[teezer250]

Hi, any advice would be most gratefully appreciated:

I have an old (circa 1970's) pumped central heating system.
One radiator had been removed during decorating (one of the two upstairs). Heating system worked.

Refitted the radiator, opened the valve and filled the radiator until water came out of the bleed vent. Heating seemed to work fine for the first night.

Next morning, heating came on, but the pump is making a "moaning/ghostly" noise and no heat from the radiators at all. Pump spinning but trying to pump air rather than water? We seem to have hot water to the taps (for the moment)!

Gone round and bled all the radiators again, until water coming out (pump off and then on). Noises stopped for a few minutes then started up again. Opened the bleed valve on the refitted radiator again but can't decide if air is being expelled or sucked in! Seems to be the same on the other upstairs radiator.

Have checked header/feeder tank in the attic: contains clean water (with sediment below the outlet).

Is air leaking into the system somewhere? And where has the water gone that was there?!?

Cheers,

A

 

[gasmarkone]

Clean water. I'm for blocked cold feed. They ain't filling.

Mark

Milk, no sugar ta.

 

[Soggy_weetabix]

oh yes. Rod than cold feed or get a u guage tube attatched to a blow torch and pressurise it out.

Do it backwards on the open vent if that dont work.

David

 

[gasmarkone]

Well David, I've done a lot of things with a blow torch, but not that. How?

Mark

Milk, no sugar ta.

PS, that brat camp's rubbish, that's why I'm here!

 

[teezer250]

Blocked Cold feed - cheers chaps, I'll see what I can do!

It's a long way from the header tank (attic) to the boiler/hot water tank (far end of kitchen in ground floor extension)...

A

 

[Soggy_weetabix]

you need the old primus bottles to do it.

Push the tube as far down cold feed as you can get it and turn on the bottle.

Hold as tight as you can!

Does work better on cold feeds that enter h/w return as they are not so hard (a lot wetter)

David