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Weil McLain Boiler System

Hope someone can help. I replaced the pump which circulates water thru the radiator system, now there is a horrible knocking noise coming from the return water pipes. I have already bled the system going to each and every radiator in the house.

Re: Weil McLain Boiler System

I'll assume you bought & installed the correct pump replacement & it's the same as the old one, and that you INSTALLED IT PROPERLY with the arrow on the pump housing pointing in the correct direction of water flow---check both of these issues out to make sure you'got the right pump & it's installed in the right direction.

Please post the model # and mfgr name of the pump---some pumps (aside from the small cartridge pumps) have a large motor on the side which is connected by a COUPLER to the impeller---if the coupler breaks (not likely on a new pump, but could happen) you will get a loud noise similar to the one you describe, but it will be located right at the pump.

That leaves the chance that there is still a lot of air trapped in the main piping near the boiler/pump & the pump's cavitating because it's pumping air.

Check the piping immediately around the boiler for AIR VENTS/spirovents, etc. that have a little screw-on cap that can be losened to get air out of the main/manifold piping---often there is also an air vent on the boiler itself.

The screw-top to these vents often have to be losened with a pair of pliers due to corrosion & are often inoperable if they've been on the system for a while.

Buy one or two of these vents new if you can't get them to evacuate air/water---they only cost $5-$10 each.

Call the technical hotline for the pump mfgr at the sites below using their 800 number if you continue to have trouble finding the problem.

Please post back.


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