Cooling system "stop leak" pellets

"96 Deville. Yeah, I know!! I have a coolant leak at top of radiator on pass side. Was told by Caddy mechs several years ago that they put stop leak pellets in system normally, or whenever they put a system back together after working on it. Can it be that I have to drain system, tighten all hoses and connections, put pellets in bottom hose, and refill system with coolant?

Vehicles come off the assembly line with a stop leak product in the cooling system. They have to do this because most of the components for the cooling system are purchased from part vendors. And since they can’t be sure if all components are 100% perfect, they use a stop-leak product. When mass producing vehicles, you can’t afford to have cooling systems leak when they’re driven from the assembly line.

As far as the stop-leak pellets? A teaspoon of black pepper works just as good.


Last time i used a product like that, I just added it to the existing coolant through the radiator cap. Your car uses a closed coolant system, and adding the pellets to the coolant reservoir should more than suffice.

However, this is a temporary fix only. With the age of the radiator, the seal is slowly going to leak even more, and may blow out when your traveling on a dark road in the middle of the night 10 miles from the nearest help. I suggest , since you know what the problem is, get it fixed right. A couple hundred for a replacement radiator now will save you months of continuing aggravating. Take it from someone who’s been there before.

Bars Leaks or Alumaseal will work for a while but sooner or later you must replace the radiator…You need to get it in the radiator, putting it in the overflow tank will do nothing…

Just my two cents worth but GM has a “special” pellet that is used whenever the system is worked on or a drain a refill. They aren’t that expensive from the dealer and you just crush a couple up and add it through the upper hose on a closed system. Don’t know how special it is but the service manual calls for the GM brand. I do think you need to fix or replace the radiator though instead of a stop leak, then flush and use the pellets IMHO.