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boiler pump not working properly(perhaps)

Postby iain1234 » Mon Sep 10, 2007 9:50 pm

we have an old boiler (olympic 20/35b) and recently replaced old radiators and installed four more. Now and again the pilot on the boiler would go out and we would have cold water for one day then everything would be fine again. Recently however, the pump stopped working, and i changed the setting from 1 to 2 and it worked for about three days and stopped working again. i then changed the setting to three and it worked for about one week. Now the pump only works if manually push the top screw and the pump is extremely hot with lots of steam escaping . The pump will then work for about five minutes and stop. The baffling thing about this is black water. everytime i manually start the pump more black water comes out. I have bled this on numerous ocassions and the water become clear, however when it stops the black water comes back. if i need a new pump, could anyone replace the pump or should this be done by an expert? Thermostat on boiler has never worked, neither has the settings which are found in the hallway.
thank you in advance for your kind response.
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Simply Build It

Postby htg engineer » Wed Sep 12, 2007 4:16 pm

A new pump is required and a new thermostat by the sounds of it.

A pump could be changed by anyone competent with working on plumbing and electrics. Could hit a few problems on the way, the pump valves may be seized on, valves may leak, airlocks if draining system.

I'd recommend changing the pump head only and leaving the pump body in place.


To renew the pump you can isolate the 2 pump valves or drain the heating system, pump valves especially the screwdriver slot one's and on older appliances tend to leak when touched.

It's a chance you can take, or leave the valves alone and drain the heating system.

There's 4 bolts holding the pump head to the body, take these out and the pump head will come loose. Ensure rubber seal is removed, and there's a new one on the new pump head.

The electrical connections are very simple, Live, Neutral and Earth.
Vent the new pump, like you have been doing to ensure there's no air trapped.
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