Boiler not Circulating

Greetings,
I purchased a home with a boiler and hydronic baseboards. When I pressurized the system there was a rapidly dripping leak inside the boiler which dripped down onto the flame. I drained the system, removed the temperature/pressure relief valve, and poured Silver King (kind of like radiator stop leak) mixed in a bucket of hot water into the system. I ran the system with the temperature dial set at 160 deg F as per instructions for two hours and although the actual temperature fluctuated between 130 and 180 during this time the drip did stop. I then put the temperature/pressure relief valve back and pressurized the system. I opened all of bleeder valves that I could but several were corroded shut and nothing came out (even before the boiler stop-leak when I pressurized the system the first time). I then drained the system and replaced four or five bleeder valves and pressurized it again. I bled everything starting from the furthest away bleeder and moving towards the closest one. The "furthest away bleeder" isn't really the "furthest away one" because water flowed backwards (opposite the circulator flow direction) through the pipes to reach the bleeders. I know this because the first water which filled the pipes was cold. When I bled everything I could feel the pipes were hot for a good distance (15 ft?) on both sides of the boiler. After 15 min or so the water was still not circulating so I bled the system and removed the circulator pump (A 1/25 hoursepower Taco 007). There was some crap in the circulator pump (not stop leak) so I cleaned it all out and dry-tested the pump for about 10 seconds. It spun freely so I put it back and pressurized/bled the system. The hot water was still not circulating. I took the wire nuts off of the circulator pump and tested them with a volt meter and it was in fact receiving juice from the boiler control unit. There is a 1" copper pipe coming from the circulator pump which splits into two 3/4" loops (one for each floor). After the split there is a valve which controls the amount of flow in each loop. I cut out one of the flow control valves to see if it was clogged but it looked clean and fully open. I inspected the portion of the line that I could see for check valves which someone may have installed in the wrong direction but could not find any but much of the line is inside walls, etc.
What gives? William
PS: If no one reads any of this because it is two long my current plan of action is to install a brand new 007 circulator ($80+tax) even though the old one worked once removed and claened. If that didn't work my next step would be to cut the lines and force compressed air through the lines to see if there is a blockage. My next step would be to meticulously determine the amount of water the system should hold and compare that to the amount of water the system does hold to ensure that there is no air left once I am done bleeding.
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How do you know it worked? The motor may be turnig, but are you sure the pump is actually pumping? Is it visible when removed so you can see it turn when the motor starts? I'm not familiar with that particular model, but the impeller may be broken, shaft broken, impeller slipping, etc. Can you (safely, of course) put the pump into a pan of water when you test it to see if it actually pumps the water?
If that didn't

Could be an air lock, but if the pump has water it sill usually push the air through. If the pump cavitates, it will not. Just be sure the pump has water when it starts. If possible, open a valve down the line to bleed it.
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Edwin Pawlowski wrote:

The circulator can be partially dissasembled and in this state you can see the impeller turning. I did not test for a slipping impeller. I did not test in water. If I remove the circulator again I will be sure to test it more thoroughly. I do worry a little bit about the water forced out of the top of the circulator in a pan causing a short but I am sure I can devise a safe way to test it.

The Taco 007 only has about 5 feet of head. I could replace it with the Taco 009 which can push 2 GMP at 30 feet of head. This would cost about twice as much but would make the system entirely "self-bleeding."
After thinking about it I think that I could make the system self bleeding with a clear water pump from Harbor Freight which I already own. The pump is only rated at 120 deg but I could use it before turning on the boiler to purge the system of air. Once I was done I could unscrew the pump and take it back with me.
1" copper ==== T ==== shutoff valve ==== T ================== | | | | 3/4" pipe | | shutoff valve | shutoff valve | | | \\====== HF Pump ======/
I think I will give this a try before switching out the existing pump.
Thank you for your time and energy, William
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