Not sure if I'm posting this in the correct place but DO NOT put this stuff in to your cooling system. I had a couple cracks in the plastic on the top of the radiator where crystallised coolant had formed (the car has never suffered from major loss of coolant) so I thought I'd give it a go and see if it would stop these small leaks. A few weeks later I noticed my cooling fan was not turning off at all, I gave it 15 minutes and it was still on so I disconnected the battery and reconnected it again and the fan had turned off, all well and good. Then one hot day stuck in town traffic I notice the temp gauge far higher than it should have been and no sign whatsoever of it dropping until I hit a straight traffic free bit of road. The cooling fan was not kicking in whatsoever. Tested fan connections to find out if there was something wrong with the fan but it was working fine. But the temp sensor (at the bottom right of the radiator) turned out to be the problem. Replaced it with a brand new one an now the overheating problems are no more but the old temp sensor was absolutely caked in brown gunk (radweld) obviously preventing the correct temperature when the fan should kick in by preventing the coolant even touching the sensor. Moral of the story is DO NOT use radweld in your cooling system. Luckily for me the temp sensor was a cheap and easy fix but if my radiator had been a bit older and a blockage in there caused by this stuff would have of been a far more costly repair. I know the saying cure the disease, not the symptoms
but I guess I learned that the hard way!
Just a heads up guys, if you're contemplating using this or not!