# Radiator pin-hole leak miracle

**URL:** <https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976>\
**Category:** Maintenance/Repairs\
**Created:** [May 4, 2022, 1:22am UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976 "2022-05-04T01:22:07Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\
**Post date:** [May 4, 2022, 1:22am UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976/1 "2022-05-04T01:22:07Z")

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My truck developed a very small pinhole leak at the very top of radiator last summer. It would leak maybe 1/2 tsp onto the ground after being run to full temp, then sitting overnight. In the fall I replaced the coolant w/fresh stuff. Since the leak was small, didn’t think any more about it, intending to just replace the radiator this summer. Never had to add any coolant. Now, this spring, I notice the leak has mysteriously stopped completely. Coolant level remains above the prior leak. Just curious, is that b/c of stop-leak additives in the fresh coolant? (Conventional yellow Prestone.)

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**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\
**Post date:** [May 4, 2022, 2:32am UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976/2 "2022-05-04T02:32:54Z")

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I fixed a small radiator leak (though much bigger than yours) with solder (acid-core) 30 years ago. It’s still holding.

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**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\
**Post date:** [May 4, 2022, 12:59pm UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976/3 "2022-05-04T12:59:49Z")

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Is the section that was leaking plastic?

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**Author:** ![Scrapyard-John](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Scrapyard-John](https://community.cartalk.com/u/Scrapyard-John)\
**Post date:** [May 4, 2022, 3:45pm UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976/4 "2022-05-04T15:45:59Z")

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> [@George\_San\_Jose1](#):
>
> Just curious, is that b/c of stop-leak additives in the fresh coolant? (Conventional yellow Prestone.)

I didn’t think coolant had any stop leak in it, but I don’t know that for certain. Hopefully the coolant system isn’t leaking slightly somewhere else (heater core, for example) and taking pressure off the pinhole in the rad so that the leak there subsided. Those old copper and brass rads (I’m assuming that this truck has) can be repaired (small leaks, anyway) like RT mentioned - if it starts leaking again.

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**Author:** ![eddo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/eddo/32/2594_2.png) [@eddo](https://community.cartalk.com/u/eddo)\
**Post date:** [May 4, 2022, 4:12pm UTC](https://community.cartalk.com/t/radiator-pin-hole-leak-miracle/183976/5 "2022-05-04T16:12:05Z")

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could be just dried up coolant plugged the hole. If so, this likely isn’t permanent.