SylvanLMP
In reply to message posted by Douglas Tedeschi:
I am disassembling three cracked radiators to make one good one. What kind of sealing material should I use at the sleeves? Right now there is something on them which is the color of orange RTV sealant. I was going to use pipe joint compound. Will that be sufficient?
Normally the steel push nipples need nothing more then lubricant for water/steam tight integrity.
You can use blue block or other type of compounds
The key is to make sure you have an equal made up push nipple on both ends of the cast Iron sections
Point of information
By the way if this is the same job your using copper tubing and copper fin for, LOTS OF LUCK trying to balancing out this system 
