Repairing Cast iron radiators

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Old 03-08-15, 12:17 PM
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Repairing Cast iron radiators

I have recently purchased and restored a couple of old cast iron radiators to be installed in my home, as they were more practical and cost effective than baseboard.

Yesterday, while installing one of the units, I was sweating pipe into the joint and heard a loud snap. Long story short, it appears that I put a hair line crack in the radiator that starts above where the bushing threads into the radiator, and runs up to the bottom of the nut that holds the radiator sections together. The overall length of the crack is about 1-1.5 inches. At the bottom of this thread, I have a picture and have marked the crack in red, as it is very hard to see.

Is it possible to braze this crack and effectively seal it, or would I be better off by searching for a parts unit and install a new end section on this radiator?

Thanks in advance.

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Old 03-08-15, 12:43 PM
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A highly skilled welder might be able to fix that radiator but it's a gamble.

As you probably realize now, any soldering within 6-8" of the radiator should be done prior to installing the male adaptor.
 
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Old 03-08-15, 03:34 PM
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Yeah, that is very strange. The funny part is that I have installed other units before, and soldered them in the same way without incident.

All of the units that I have acquired, have needed to get torched to red hot in order to wrench the old fittings out so that new ones could be installed. In this particular instance, what cause the rad to crack? When it did this I had only began to heat the pipe fitting up to be soldered. The radiator section was still cold to the touch.

When I acquired these 2 rads, I believe the warehouses I looked through may have had other ones like it. Would I be better off getting one of those and just replacing the end section?

On another note, one of the other rads I installed this time has developed a leak at the bushing that threads into the rad. It appears it is getting past the threads in a couple of spots. Would you have any suggestions to repair this leak? I was able to drain water off of it and get 1 more turn out of the bushing, and that seemed to slow the leak down significantly.

But, to fix this properly, I would assume that the rad would have to be pulled, and the fitting re-installed. Would it be recommended to re-install the bushing with tape, dope, etc? Any advice is appreciated.
 
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Old 03-08-15, 04:41 PM
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First off you should always solder the pipe to any threaded fitting and cool before attaching yo anything. Not doing this is the number one reason for thread leaks on a copper adaptor.
Forget about replacing the end section. You probably cannot find new push nipples which is what makes the sections water seal.
 
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Old 03-08-15, 04:50 PM
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One turn on the bushing "helped some" - it seems you need more turns. It is easy to underestimate the torque needed for a leak-free threaded connection.

Yes, if you remove and replace a bushing, use dope or Teflon tape.
 
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Old 03-08-15, 05:03 PM
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And when you use tape, PLEASE don't use more than two wraps! No matter what you see or hear or read on the internet... hey, wait aminnit... that means here too! OK, but still, more than two wraps is TOO MUCH and it can prevent getting the desired METAL TO METAL seal on the threaded connection.
 
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Old 03-08-15, 05:48 PM
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Thanks for all of the replies. It is greatly appreciated. There are a couple of items that I would like to further elaborate on.

1. The leaking fitting that I mentioned is the bushing that screws into the radiator itself. I had replaced this fitting initially, but it seems that I just didn't get it tight enough when it was first installed in the rad. It appears that since the rad has been heated up a few times that it caused the metal to expand which enabled me to get another revolution out of the bushing. I will need to remove the rad at a later time and tighten the fitting.

2. As for installing a new end section on the cracked rad, it was mentioned that the push nipples would be hard to come by. Are these not the right ones?

Radiator Push Nipples


When these old rads were installed new, werent they built onsite? The sections were hauled into the space, then the rads were assembled? I always thought it would be neat to actually build a rad....... or at least replace a section....



Please let me know your thoughts.
 
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