I have heard a few different ways to fix a pin hole leak in a radiator. I have heard put a small amount of black pepper in the radiator, or use jb weld to patch the hole, and not to use the stop leak antifreeze.

Any suggestions?


If you are willing to drain the coolant, most radiators can be brazed or welded to fix pinholes.

  • does this include aluminum radiators? – BrettAdamsGA Jan 24 '12 at 16:27
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    Aluminum radiators can be welded by someone who knows what's they're doing. – Timo Geusch Jan 25 '12 at 0:28

If I didn't really care if I might hurt the car, I might be willing to try JB Weld...

  • Seconded. At worst you'll ruin an already-dead radiator, not any other part of the car. I've had luck with this method in the past, although it was a giant gaping hole and I added some radiator stop-leak too after using the JB weld. – R.. GitHub STOP HELPING ICE Jan 25 '12 at 5:18

I've fixed radiators in the past, but unless your car is one where the replacement radiator is really expensive, you're probably better off just replacing it. A new radiator will usually give much better cooling performance. Last time I replaced a radiator is was just $70 or so...


Many years ago, I brazed my non-aluminum, non-plastic radiator pin hole shut with a metal coat hanger and disposable propane hand torch. Never had a problem again with that radiator and it lasted for many years.

Otherwise, scrubbing with acetone and using JB Weld "Extreme Heat" and a piece of metal flashing might be worth a try (follow safety procedures).

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