Bars stop leak for radiator? Does it work?

If this is the plastic tank part DO NOT use the JB weld plastic tank repair kit, IT DOES NOT LAST. You can use just the JB weld waterproof epoxy and it holds better. make sure you clean the crack up to get rid of the glycol or antifreeze before you apply it.

 

Not sure what you are trying to stop leaking, if it's plastic, that crap is so cheap, nothing sticks, so just replace what's leaking. For internal fixes, I SWEAR by a product called "Mend-Tite", a Zecol product. It's not the old "pepper flakes" crap, but a polymer that stays liquid in AF, but when hits air, like a leak, it hardens. I've used Mend Tite several times, mostly as a temporary fix, and it never leaked again AND doesn't plug heater cores. Mend-Tite,,it works!
Zecol Mendtite Heavy Duty Radiator Seal

 

How about k-seal

 

The reason nothing sticks to plastic is it has a release agent applied to it during manufacturing, so it will come out of the mold. That release agent in still impregnated into the plastic, hence nothing will stick.

 

i used that stuff to limp my truck home 1200 miles after blowing the head gasket. not sure it is really designed for trucks because of how much load is put on the engine when hauling 80k pounds it doesnt ever really seal up.... but to get it home it does the trick... it can completely seal up a head gasket on a car engine pretty well and good for the next 100k miles or until u run into overheating issues lol

 

Adding this stuff isn't going to help. It may fix the leak but it will more then likely cause other issues later on. More then likely will clog other coolant passages

 

All this "snake oil" is nothing more then mustard powder. The "magic" based on properties of mustard powder to stick where flow current is slow and particles swell. Ask your doctor about thrombosis. The very same you will do to the engine.
Can you trust to someone who did and regret ?

 

If it's the radiator and not the radiator top tank, that is also plastic on some, give Mend-Tite a try. I think Bumper to Bumper has it, or did. No, I don't work for Zecol, but in all my years, it's the only thing that worked. Large capacity might require 2 bottles. Let us know, eh?