Heat-resistant sealant for chimney flue?

[Geoff W.]

Hi all,

My diesel heater chimney appears to be leaking. Outside looks like a thick bead of carbonization pretty much everywhere there's an edge to be carbonized. Guess it's time to decoke and re-seal.

Anyone have a sealant recommendation for something that works for this? Bonus points if it is applicable in cool weather... I want to stop the leak but we have a particularly cold spell setting in. Or, ideas for stopgaps?

Thanks,
Geoff

 

[Loren Beach]

I recall seeing something black seeping out of joints on a boat with a bulkhead diesel (older) heater. I wonder if this is creosote? (condensing out?)

 

[Geoff W.]

I believe it is, Loren. To be more clear, there is definite coke buildup on the outside but it is leaking rainwater into the cabin right now... Down the outside of the chimney, not the flue/chimney gap.

 

[Afrakes]

High temp sealant

If you want to be able to take the pipe sections apart use Mill-Pac. In our business we use it to seal metal gas vent. It works at any temperature. You can also use RTV red silicone. The problem with that is it makes it very difficult to get things apart again.