To use or not to use radiator leak sealant?

I have a 1986 Subaru with a pin hole leak in an original equipment radiator. They want $350 for a new radiator - is it safe to use the liquid radiator sealant to stop a leak?

Put a teaspoon of ground black pepper in the radiator. This will stop the leak just as good as anything you can buy off the shelf. Ive used this to stop external head gasket coolant leaks and it lasted a year in some cases.


I’ve used it in an emergency (camping in the woods in Maine), but later had the radiator repaired properly. My grandfather used oatmeal in his Model A Ford, which, I believe, did not have a water pump, and relied on natural circlation.

Go with Tester’s suggestion. It will be cheaper and it is less likely to clog up the system somewhere else.

Powdered sealer can clog crucial orifices as easily as clogging a pin hole, so why shouldn’t liquid sealer do same; or pepper? ONE OF MANY crucial orifices: “spray holes” around cylinder that cool cylinder “hot spots”. Not so crucial orifices: tubes in heater core- (no heat). Call a garage you trust or maybe a Pep Boys and ask what the best radiator shops in the area are. (A pin hole seems to be repairable versus

a seam.) If first radiator shop says they can’t fix leak, ask for a price on radiator- parts and labor. (Just parts if you’re gonna install radiator.)Then tell’em you’ll sleep on it. Now go to 2nd radiator shop. (you see, some radiator shops balk at fixing leaks 'cause they’d rather sell a radiator.) If 2nd shop says leak’s not fixable, assume it can’t be fixed and get their price parts and/or labor. Cheapest

radiator prices I’ve ever seen are at radiator shops. If you do decide to use sealer, start w/maybe 1/4 container at first. Put 2 gal. of antifreeze and containers of sealer in your trunk. If soon you see you need more sealer, add a little more. Object is TO USE AS LITTLE AS POSSIBLE. Good luck, KS P.S: “Pennywise dollar foolish”, pardner.

Did you know that most auto manufacturers put BarsLeak in their new vehicles cooling systems when they come off the assembly line?

Read it here


You could remove the radiator and solder the pinhole with a propane torch.

Yep, keith. Make sure you use acid core solder, not rosin core.

I agree, either fix it or replace it. Forget the “stop-leak” stuff.

New radiator if the car was worth saving. Use the pepper or the sealant.

Radiator “Stop Leak” products do work to a limited extent however: remember, if it stops the leak (clogs up the hole) it is also clogging up something else.