Bars Leaks for radiators - how well does it work & perhaps last?

Hey there, Seeking Wisdom of this List.

Thinking about applying Bars Leaks Liquid Copper to solve a coolant leak. Any experience out there with Bars Leaks for cooling/heating system leaks?

I have a 2000 Dodge Caravan with a fast (2 drops/sec) coolant leak that seems to come from the Heater Inlet Tube Assembly (see that is not easy (time or expertise) to get to. It has O-ring seals and I think that’s what’s failing. I’ve read other accounts here and elsewhere that mentions that these tubes rust or that the O-rings fail.

I can’t see wherever the point of leakage is, even with the help of a mechanic and a lift. He suggested Bars Leaks.

Help with Bars Leaks advice, please.

For repair advice other than Bars Leaks, please see my original post here: 2000 Caravan 3.0 V6 leaking coolant, overheating

Thanks in advance.

Add a tablespoon of black pepper to the radiator when the engine is cold. Then start the engine and let it idle until the leaks stops.

I did this on my Beretta when the head gasket sprung an external leak. The fix lasted a year before the head gasket had be replaced.


It works for a short time if the leak is not severe.

Years ago I was camping in the woods of Maine, and the Malibu V8 sprung a leak in the rad. I temporarily removed the radiator cap, topped up the system with water and carefully drove to the nearest service station available. The attendant put in a can of Bars Leak and told us to get the radiator fixed as soon as we got home, 700 miles further West,

We did as instructed, and the fluid had stayed right up for the trip home while pulling a camper.

So as a stop gap it works

I have used the original pelletized Bars Leaks stop leak for radiators many times on small leaks. All of the fixes were permanent.

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I strongly suspect the answer (that you might not like) is “it depends”.

And in case my anecdote with a '99 T/C minivan with a 3.8L helps you, here it is:
-mysterious very slow and intermittent leak, seemingly near waterpump area after radiator replacement (due to crack in side tank)
-used Alumaseal (powder, and no interest in that product or its company) according to instructions and leak stopped for over 18 months (close to 2 years)
-leak suddenly returned as much more significant (although still intermittent) and obviously from waterpump; turned out to be leaking thru seal around the shaft of the pump

my takeaway is that if it helped seal around a moving shaft, it worked much better than I expected

I don’t see how bars leaks is going to fix a leak due to an o-ring that is split in half . . .

If you use it, read the instructions first and follow them. Some other things have worked well by doing that.

Of course, a sealant such as Bar’s Leaks is NOT the solution here. A sealant is also likely to plug up an old radiator, resulting in more serious overheating problems.

As I already pointed out, what happens on this engine is that the steel crossover pipe becomes corroded away in the area where the O-rings seat. This pipe is made up of two parts: one connects directly to the water pump with an O-ring, then the two parts connect to each other with O-rings. The second part connects to one of the radiator hoses.

By the time this pipe has enough rust to leak, it leaks because the O-ring(s) must seal to surface(s) which are pitted and out-of-round. No sealant can possibly fix that.

Replacing the crossover pipe is not much harder than changing the timing belt and water pump (which is fairly difficult on this engine), and should be done at the same time.

The original pelletized Bars Leaks is an organic product which swells up ONLY when it dries out in contact with air. It does not plug things up.

Thanks to all for the comments. I thought there would be some mixed feedback and I appreciate every comment.

I’ve probably driven 300 miles since my original post. Here’s what happened since.

For a few days, I could not put in any of the Liquid Copper Bars Leaks for Radiators as I had topped up the radiator as well as the reservoir. As the reservoir would go lower and lower, I was finally able to put in about 1/3rd of the Bars Leaks in the cooled radiator.

Since then, I’ve been able to add more to where I have about 1/4th of the Bars Leaks remaining. Every time since then that I get to check the cooled radiator, it has been full. There’s about 12 OZ remaining in the reservoir. This has been the same for about 4 days now.

Will report back in a week or two if nothing much changes, sooner if otherwise.