Pump at fault?

[HubbyStew]

Hi, hopefully someone can solve my problem as I'm now completely frustrated after 2 days. Boiler serviced in summer and when system restarted to bleed radiators the boiler kept overheating. Engineer found cold elbow inlet to pump was almost completely blocked up with black solid sludge so replaced. On bleeding radiators 4 upstairs and 3 downstairs, 2 on end of one run weren't heating up. Drained whole system and ran with Sentinal X800 for 5 days. Flushed system, removed 2 suspect radiators and flushed through with hose until running clear. Reconnected radiators filled system, all but same 2 are heating nicely. Closed all upstairs and single downstairs one at end of line, and then drained system again. On refilling, the 2 radiators heated up nicely and were working perfectly. I then proceeded to turn back on the other radiators, bleeding as necessary. Remaining rads heat up nicely, but then the 2 downstairs have stopped working again. I've had system running while draining thought valve on feed to 2 warm radiators and I get all pipes to and from red hot, but still to no avail and they get lukewarm at best. I'm wondering now whether the pump is to blame, as it is very hot to touch and has obviously been having to deal with a pretty sludged up system for some time/struggling to pump water through a partially blocked union.

Any suggestions gratefully received.

Thanks

 

[ollski]

argh, long post disappeared

 

[Agile]

The pump will get very hot if there is no flow or if it is either jammed completely or turning very slowly.

See the FAQ on how to check the speed.

Then perhaps to remove the head to see if the impellor is blocked.

Tony

 

[HubbyStew]

Pump failed last night, so replaced, balanced rads and full system working.

 

[JohnD]

you might consider a system filter. The cleaner will have dislodged and loosened sediment, you can never drain it all out.