Radiator Stop Leak Tablets (HDC)


Radiator Stop Leak Tablets


  9 Reviews

Bar’s Leaks Radiator Stop Leak Tablets inhibit the formation of rust and scale, neutralize pH imbalance, control electrolysis, lubricate and seal internal, external and coolant-to-oil leaks. Imagine getting that range of effectiveness in a product you can buy off the shelf rather than through service only a mechanic can provide. In fact, this is the same product that’s been used right on the assembly line by OEM automakers around the world for 30+ years. This solution is the result of careful research and testing on the part of our team of top-flight chemical engineers. They work each day to improve existing products like our radiator leak repair tablets, as well as to develop new products to keep up with the latest in automotive innovations and technologies.


NOTE: Cooling systems that are dirty or partially clogged should absolutely be flushed before usage.

  1. Remove radiator cap when engine is cool.
  2. Install two (2) tablets in radiator for each gallon of cooling system capacity. If vehicle does not have a regular radiator cap, remove top hose where it attached to radiator and insert tablets in hose and then reinstall hose. Tablets may be crumbled or pre-dissolved for easier application. NOTE: Most vehicles will use all six tablets.
  3. Fill radiator and reservoir to proper level.
  4. Reinstall radiator cap.
  5. Drive/idle engine for 15 minutes at normal operating temperature.
  6. If leak persists, a second application may be necessary.

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Our product engineers created these Bar’s Leaks Radiator Stop Leak Tablets to repair radiator leaks from within so you can get back on the road in no time. These tablets might not be able to surf the web, but they are definitely more powerful than you think. But what our radiator leak repair tablets offer in effectiveness, they don’t sacrifice in usability or affordability. In fact, you need no special automotive expertise to apply our tablets to repair radiator leaks.

Your leak’s days are numbered. Pick up a pack at your nearest auto parts store and make sure you watch our how-to video for an easy step-by-step installation process.


Whether you need radiator leak repair or to stop a leak related to head gaskets, engine oil, power steering, transmission or other auto components, Bar’s Leaks offers a full suite of time-tested, customer-proven solutions. We offer chemical repair products for a variety of automotive solutions, each designed to represent the utmost in affordability, usability and effectiveness. While you can find a number of product alternatives that claim to repair radiator leaks, you won’t find the same level of effectiveness — and sometimes these other products make your situation worse than before.

Made right here in America, just an hour outside of Detroit, radiator leak repair products from Bar’s Leaks are the latest in a nearly 70-year history of creating chemical repair solutions for everyday drivers. We strive each day to live up to the legacy of service and effectiveness that tens or millions of customers have enjoyed through our many decades of operation. When you want the best in radiator leak repair solutions for your vehicle and the investment you’ve made in it, choose Bar’s Leaks.

Get the product you need for repair of your radiator leak today.

Customer Reviews

  9 Reviews
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 9 reviews
 by Daniel R.
Been using Bar's Leaks for a long time

I have been using Bar’s Leaks Stop Leak Tablets (HDC) on my radiators since the 1970’s. I have never been rich so anything that works perfectly fine on my vehicles without having to replace the whole radiator makes me a happy man!

 by James
It works!

I had a moderate coolant leak I couldn’t trace to the source. Probably from a leaky gasket, hose, or fitting that was variable depending on engine temperature and pressure. I flushed the system, dropped in some pre-dissolved tablets and filled back up. PROBLEM SOLVED! 😀

 by Dennis
intake gasket leak

I had a small leak at the intake gasket and after putting in the tablets the leak has stopped. After 2 years it's still holding.

 by David M.
Tiny Leak

I had a tiny coolant leak and we could not find it using the pressure test method at the shop. My mechanic said to get some sealant so I had purchased the Stop Leak 2X concentrate and called the tech support line for help in using it. Fred suggested the tablets instead. Following his suggestion I added three tablets to stop this tiny coolant leak. It's been 72 Hours and there have been no further leak droplets on the driveway. Thank you for your advice on using your products.

 by Thomas I.
The best sealer period

I cracked my 460 block when I was racing went into the pits and put in  some Bars Leak's part number HDC, nicknamed the horse pills. It sealed a 4-inch crack and was able to make the next round. I swear by this stuff.

 by Hank Flores - Phoenix, AZ

Per your suggestion I ran 12 packs of your "Bar's Leak" tablets through my heating system for 48hrs. I reconnected my heater, purged the system, added 2 new tubes, and heated my water to 110 and its working great. Please tell Fred on your Tech Support team "Thanks for the phone call and like the Nautilus, Bar's Radiator Stop Leak Tablets got me through the cold spell in Phoenix.

 by M. L. - Aspen, CO

I operate two 300 hp boilers for the purpose of melting snow on the plaza area of Aspen Highlands ski area. This fall we discovered several small leaks on the fire tubes of the boilers. The repair cost to have them welded would have broken our budget. Remembering the story of the USS Nautilus, my co-worker brought up the possibility of using Bar's Leak. 2500 tablets later (the preventative maintenance dose) and our boilers are no longer leaking. You have a great product! Thank you!

 by Rev. D. Stubbs - Fort Valley, GA

On behalf of the congregation at Fort Valley First Baptist Church, I would like to extend my heartfelt thanks to your company for providing the stop leak for our boiler system for the last three years. Our system is approximately fifty years old, and with the additive, we are able to safely use it each year. Your cooperation and generosity are much appreciated!

 by J. Taylor - Richmond,Va

Work magic in less than 20 mins. I used epoxy puddy on the outside of my radiator leak. Drove around and let it cure. Still was leaking. Added 4 tablets(crumbled) to my radiator. Drove for 15mins. Check the area..no more leaks. Awesome product thanks.

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