Kalimex K Seal, unlike all the others it contains silicone, although intended as a temp cure, I personally know cars that have had it in for over 5 years still not leaked a drop, despite having anti freeze changes.
Have also used it on a nissan 4wd with a cracked(frozen) block over 10 years ago still water tight.
I used it myself when my HG went shortly after getting my car, it bought me time to get the job fixed properly but hadn't leaked a drop in 8 months with it in, after going through one winter.
It also did not block the heater matrix not a bit as it only reacts with air.
tabetha