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.
Last edited by NashuaTech; 02-13-2009 at 10:01 AM.