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reosw · 01-21-2021, 01:52 PM

I have what appears to be a pinhole leak in a less than 5 year old radiator, thus I would like to try a stop leak product prior to replacement. Research has shown that Zerex Super Sealer is approved for the Cummins ISL. Question is, lacking a radiator fill cap (only the expansion tank) how and when (hot or cold) does one introduce the sealant to the cooling system ?

hclarkx · 01-21-2021, 02:20 PM

I'm not experienced with this product. However, my engineering sense is that putting it in the expansion tank is sufficient. As the engine cycles between hot and cold, coolant moves into and out of the expansion tank. After some cycles, the liquid in the expansion tank will have mixed well with the coolant in the engine and radiator.

As such, it might take a couple of engine thermal cycles for the additive to be fully effective.

**CountryFit** · 01-21-2021, 02:24 PM

Do you know what material your rad is? If it's aluminum, you might want to assess if a welder can patch it up.
(I wouldn't feel comfortable with that kind of sealer in a large system. Who knows where it's going to stick to. But, if you are determined to do it, disconnect the hose after the thermostat (coolant flow per se) and pour in. At least it won't go into engine directly but to the rad.)

reosw · 01-21-2021, 02:43 PM

Im pretty certain is it aluminum, but by the time the labor to remove the radiator was completed, I might as well replace it. It is buried between the intercooler and AC condenser coil, which also makes it difficult to find the source of the leak, but it is a pain considering the original lasted 12 years. 1 quart of sealant treats 4 gallons so 2 should come close, assuming I have about 10 gallons total in the system.

hclarkx · 01-22-2021, 01:35 PM

Back about 1961 my Mom's Pontiac sprouted a major leak in the radiator core. Easily 1/16". We put in a tube of alumaseal. The leak stopped within a minute and that radiator was still in the car 12 years later when she sold it. I did a duckduckgo on it and darned if it isn't still on the market. It consisted of a tablespoon or so of very thin aluminum flakes.

Dav L · 01-29-2021, 09:18 AM

I wouldn't put any "stop leak" in that expensive radiator.
Fix it right. The real question is why is a 5 year old radiator leaking.
Is there a brazing defect? Or something hit it? Or vibration due to mounting wrong?
If there is one, what about all the others that will start?

Or is it really just a clamp that is loose?