Re: Liquid head gasket repair.
Because I'm a dirt cheap guy that was broke for most of my life, I have used a lot of..."backyard fixes" over the years. I'd never recommend others to do it, because half-assed is a great way to describe them, but they worked for me.
But gasket sealers...yes, to a degree. I've used the K&W sealer on a few motors I didn't care about, the kind where I'm planning on pulling the motor anyways, so at worst I'm out $20 and a couple hours of my time if it doesn't work. If it does, hey, maybe it gets me through the winter so I'm not freezing my berries off while pulling the motor to fix it the right way.
It worked on the small leaks. The kind where you're topping off the overflow bottle every other week or so. The leaks where you're lucky to make it to 15 miles to work without overheating...not at all.
I found it also isn't a great plan if you have modern aluminium radiators with the small tubes, as it can plug the tubes just as well as the head gasket. Same thing here for the radiator sealers. I've used that powdered aluminum radiator sealer in a lot of vehicles, and plugged a few radiators too well doing this too, lol. Once as a teenager, I even plugged a water pump with that stuff on my old Grand Am, though at that point I didn't know about weep holes on a water pump, and just kept pouring more powder in the radiator.
But same thing - worked well on the small weeping leaks, but anything bigger it didn't do anything useful, and unlike what the instructions often say, if one doesn't do it, no amount of further treatments will help.