# Have you ever used Stop Leak for a car radiator? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [March 9, 2008, 6:29pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743 "2008-03-09T18:29:00Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [March 9, 2008, 6:29pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/1 "2008-03-09T18:29:00Z")
Have you ever used Stop Leak for a car radiator? My car has a pin-hole leak. Less than a quart of fluid lost each week. Definitely the radiator (it was tested by a professional.) Rather than replace it, I’m thinking of trying the stop-leak. Has anyone here used it? What was your success rate? ---
**Author:** ![user\_hostile](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/user_hostile/32/474_2.png) [@user\_hostile](https://boards.straightdope.com/u/user_hostile)\ **Post date:** [March 9, 2008, 6:51pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/2 "2008-03-09T18:51:49Z")
It’s been posted before, but another name for it is, “last rites”. My experience with the stuff is has always been as way to delay the replacement of the radiator. It’ll work, but other leaks are bound to appear. Two types I’m aware of are the cellulose which kind of plugs up the leak like toilet paper in an elementary school bathroom, while the other is metallic beads which as a WAG seals up the leak by plugging up the leak and then electroplating (“corroding”) around the hole enough to seal the leak. Other Dopers can prove me wrong; please fight my ignorance. I found the metallic beads to be more durable. But come winter, I always noticed the heater coil was far less effective, regardless of the stuff I used. Good luck. ---
**Author:** ![CynicalGabe](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@CynicalGabe](https://boards.straightdope.com/u/CynicalGabe)\ **Post date:** [March 9, 2008, 8:34pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/3 "2008-03-09T20:34:58Z")
Temporary fix: Take a cigarette and dump all the tobacco into the radiator. No paper, just the 'baccy. ---
**Author:** ![Winston\_Smith](https://avatars.discourse-cdn.com/v4/letter/w/e95f7d/32.png) [@Winston\_Smith](https://boards.straightdope.com/u/Winston_Smith)\ **Post date:** [March 9, 2008, 8:43pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/4 "2008-03-09T20:43:58Z")
You could save a couple bucks and just put a teaspoon or two of pepper in the radiator instead of stopleak. I’ve done this in the past, but it’s worth repeating you’re probably only postponing the inevitable replacement of your radiator. ---
**Author:** ![Mrs\_Johnson](https://avatars.discourse-cdn.com/v4/letter/m/7cd45c/32.png) [@Mrs\_Johnson](https://boards.straightdope.com/u/Mrs_Johnson)\ **Post date:** [March 9, 2008, 9:35pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/5 "2008-03-09T21:35:11Z")
I’ve used Stop Leak as a temporary fix until I could afford a new radiator. I’ve never heard of pepper or tobacco… that’s interesting. ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [March 9, 2008, 9:37pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/6 "2008-03-09T21:37:51Z")
I used to work in a Checker Auto store. I have seen these products work before on many occasions. Having been in the automotive business for a long time I wouldn’t use them myself but as a temporary fix they do work. There is a product called Bars stop leak. It has all manner of stuff in it that can plug holes, it usually works best for heads gasket and core plug leaks. There is another product called Alumaseal which is ground aluminum and works good on radiator and heater core leaks. I haven’t worked in the aftermarket side of the auto industry for 20 years so there may be even better stuff out there now but these products I’ve mentioned do offer temporary fixes. Nothing can replace fixing what is wrong, however. ---
**Author:** ![Marienee](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@Marienee](https://boards.straightdope.com/u/Marienee)\ **Post date:** [March 9, 2008, 9:48pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/7 "2008-03-09T21:48:58Z")
Bars leaks is great stuff. It does only postpone the inevitable I suppose but it did postpone it for several years, which was okay with me. Only you have to clean it all out and put some more bars leaks in every, um, I think it was once a year. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [March 9, 2008, 11:26pm UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/8 "2008-03-09T23:26:12Z")
I’ve gone a couple years with no leak after using it. You eventually will have to replace the radiator. Don’t let them have it repaired. My parents did that, and it leaked soon after again. ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [March 10, 2008, 2:44am UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/9 "2008-03-10T02:44:47Z")
Perhaps the most legendary success was its use in the USS Nautilus back in 1958. [http://www.barsproducts.com/bars\_history.htm](http://www.barsproducts.com/bars_history.htm) The article doesn’t mention it, but even when the Nautilus was decommissioned in 1980, the leak in the steam condenser was still sealed. ---
**Author:** ![zenith](https://avatars.discourse-cdn.com/v4/letter/z/e19b73/32.png) [@zenith](https://boards.straightdope.com/u/zenith)\ **Post date:** [March 10, 2008, 3:02am UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/10 "2008-03-10T03:02:16Z")
My experience with Bars Leaks and Alumaseal is that if either one works, it works right away and stays working 6 months to a year. Putting more and more stuff into a radiator that doesn’t seal right away just steals money away from the purchase of a new radiator/core. Antifreeze @ $8/gallon and up gets expensive. If you see muddy-looking crap in the radiator of a used car you’re considering, assume the mud to be stop-leak, not “just dirt”. If you agressively flush a “dirty” radiator whose history is unknown, your new antifreeze is likely to leak from a dozen places. Either plan on a new radiator annd/or a new heater core real soon or walk away from a “dirty” radiatored car. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [March 10, 2008, 3:15am UTC](https://boards.straightdope.com/t/have-you-ever-used-stop-leak-for-a-car-radiator/440743/11 "2008-03-10T03:15:10Z")
There are only two brands I will use in my customers’ (or my) cars - Bar’s Leaks, and GM seal tabs. Both are used by car manufacturers as a factory supplement during assembly. Either can be very effective in sealing small leaks and seepage. Neither is expected to last forever; lasting until the next coolant flush is due is perhaps the most one should hope for (no guarantee on that, of course, but it’s not an reasonable hope). I have seen Bar’s leak stop a “pissing stream” leak from a water pump, while the engine was running, in five minutes. It lasted six months. I have seen it stop radiator leakage for two years. I have also seen it not help at all, but it’s a cheap gamble to make. There have been cases of radiators and heater cores becoming internally clogged by leak-stop products. If that happens, there’s no cheap fix – you gotta replace the affected part (possible but unlikely exception being an old-design radiator that can be “rodded out”). I have never seen Bar’s Leaks cause that over a 35 year career. However, any brand or substance other than the two I’ve mentioned would worry me.