My heater core has a slight leak - it is a massive job to re/re and no mechanic around here wants to do it, but very simple to isolate the heater core. I have a bottle of Liqui-Moly Radiator Stop Leak, and it looks like it requires heat to activate based on the instructions.

I was thinking of isolating the heater core, flushing it with water and then using the stop leak as a temporary measure.

Does anyone have any clever ideas as to how to activate the stop-leak with an isolated heater core? (No way am I letting that stuff get anywhere near my engine - I’m only considering it as I have nothing to lose since if it doesn’t work, the heater core has to be replaced anyways.)

I have heard of stop-leak working for years in some cases which is why I’m wanting to try it.