Radiator Problem


I have a small radiator leak the only way one can see it is a slight steam that is barely visible. Has anyone ever used the radiator stop leak junk that you can put in your radiator to stop small leaks? Is this harmful to other things like heater coils, water pumps, etc.? Any info is appreciated.


Just put a teaspoon of black pepper in the radiator. That’ll stop the leak.



Stop leak works by congealing and hardening when it comes in contact with the air as it passes through the hole. It also can congeal and harden when it comes in contact with any air the might be in your system.

Pepper simply clogs the hole until it blows through. And makes the coolant taste better.

Leaks are usually caused by corrosion. Corrosion continues even if you plug the leak. We had one poster that plugged his leak with StopLeak, the system was then able to bring the coolant up to its full correct pressure, another corroded spot blew out, the engine overheated, and the engine suffered serious damage.

Why would you not want to replace the radiator? Why risk losing your engine for the sake of a few hundred bucks?


I agree with mountainbike 100%. Get the radiator replaced. Do not try to fix it.


Mountain is right. The only valid use of leak stop is to fix it long enough to drive to the shop. The problem is you never know when it is going to fail and it will. It also can clog up other parts of the cooling system. Keep away from that stuff.

Tester's suggestion is not as bad as the leak stop and it is far less likely to cause other problems, but it also suffers from the "it is going to fail sometime and likely it will before you finally bring it in for a real repair.  

James46 car is maybe the best possible candidate due to the type and size of the leak.


Doesn’t anyone know that every vehicle that comes off the assembly line has a stop-leak product in the cooling system?

This is because the radiators and heater cores are purchased from vendors, and when a vehicle comes off the assembly line and is started, the last thing that wants to be seen is a coolant leaking from the new vehicle.



I agree with the others, just replace the radiator and don’t play with that junk.


The slight steam could mean that the radiator is old and ready to be replaced; especially if you are seeing green and white on any part of the radiator.