I used #290 to seal several pinhole leaks in my Rob Roy boiler. Worked very well. The temp range for #290 is up to 300F. Steam temp is 324F @ 80 PSI, 350F @ 120 PSI. I realize these temperatures are higher than the working temp range of the loctite. However, my belief is that those temps are for failure of a Joint. To seal a weep in the boiler you just need to get a sealant into a very small gap. There have been many "fix's" for weeping leaks such as ginger etal. The reason I chose wicking loctite is because it will wick into the gap. Loctite #272 is rated up to 450F, but I don't know if it will wick in as it is recommended to apply before assembly. My gut feeling is it would wick enough to seal a minor leak. Just my thoughts.