Pelletized Heavy Duty Stop Leak (PLT11)

Pelletized Heavy Duty Stop Leak


  39 Reviews

Our original, legendary pelletized formula. Simply put, it’s the tried-and-true fast, effective, easy-to-use powder formula radiator stop leak that’s just as simple for a regular driver as for an experienced mechanic. Convenient solutions to seal coolant leaks shouldn’t be limited to just those with advanced automotive knowledge, which is why each product in our catalog is designed to meet the needs of anyone who gets behind the wheel of a vehicle.

DIRECTIONS (IMPORTANT NOTE: Cooling systems that are dirty or partially clogged should be flushed before use):

  1. Allow engine to cool so radiator cap can be safely removed.
  2. Shake well and pour directly into radiator. Do not pack pellets in radiator. Pellets may be pre-dissolved if necessary by putting them in hot water. Note: If you don’t have access to radiator, remove top hose where it connects to top of radiator and install product in hose. Reattach hose and tighten clamp.
  3. Fill radiator and overflow tank to proper level, reinstall radiator cap and drive or idle engine for 15 to 30 minutes.

Leave product in cooling system for preventative maintenance. Use once per year to help guard against future leak development.

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Our Bar’s Leaks Pelletized Radiator Heavy Duty Stop Leak is specially formulated to seal larger leaks better than other stop leak products. You’ll find plenty of powder formula radiator stop leak products on the market, but you won’t find a seal coolant leak solution that beats ours in effectiveness. Our Pelletized Radiator Heavy Duty Stop Leak is versatile, too, working safely and effectively on plastic, aluminum and metal radiators, heater cores, gaskets and freeze plugs. It also has a water pump lube that lubricates water pump seals and inhibits the formation of rust and scale.

In under an hour, you can quickly and easily solve that once-dreaded leaky radiator. Give it a try and get your car back on the road in no time.


Not every product that claims to stop seal coolant leaks actually works as advertised. In fact, many of the products actually can make the situation worse. But, at Bar’s Leaks, our powder formula radiator stop leak and other products are developed by the best chemical engineers in the industry. These products are proven to alleviate leaks related to cooling systems, head gaskets, engine oil, power steering, transmission and other vital components. The goal with each product is to get you back on the road as quickly and affordably as possible.

Our history of serving vehicle owners stretches back nearly 70 years. Our status as the industry’s best-known brand has emerged from our long track record of successfully developing products that are easy for everyday drivers to use. Bar’s Leaks manufacturers its products right here in the United States, just an hour outside of Detroit. When you want to mild and moderate stop seal coolant leaks at the fraction of the cost of taking your car to a professional, choose powder formula radiator stop leak from Bar’s Leaks.

Learn where you can find Bar’s Leaks Pelletized Heavy Duty Stop Leak near you

Customer Reviews

  39 Reviews
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 39 reviews
 by Jason Z.
Your products are awesome

I used this stuff because I had a chunk of gasket blow out from my water pump and the piece that blew out was big enough to slip a dime inside there. So I was very skeptical on whether or not this stuff would work because I've never had any other stop leak product work for me...and I'm completely shocked because it completely worked, not a single drip came out and it's still holding today. I would just like to say that Bar's Leaks, you are awesome, your products are awesome, and I will recommend them to everyone I know. Thanks again because I really did not want to have to put a new gasket on that water pump.

 by Joseph M.
Your product just saved me $700

My 2013 Chevy Malibu's water pump started leaking. I went online and your products came up. I bought two of your stop leak products. One was $3.89 the other $8.89 at Walmart. I did not have much room in my radiator so I used the smaller one with the pellets. I have the larger one in my trunk for further use. I am on day five and no leaking. My mechanic says a new water pump will be almost $700. I am 82 years old on a fixed income and your product just saved me $700. Thanks again.

 by Rodney H.
My go-to leak product

I had a radiator leak and knew from past experience to get some Bar’s Leaks Heavy Duty Radiator Stop Leak PLT11. It worked perfectly the first time just like before.

 by Juanita R.
Would recommend to anyone

I started using Bar’s Leaks when I was young. I am 63 years old. I used to use it in my radiator. It really worked. My car was old but it kept going for about 6 months until I got it fixed. I would recommend the Radiator Stop Leak PLT11 to anyone.

 by Gabrielle
Worked like magic

I had a 2012 BMW X5 that had a coolant leak. I was in a bind – I had to take a family member to the hospital which was a couple of hours away and did NOT have time to take the car in first, but what to do? I called a friend who recommended your Pelletized Heavy Duty Stop Leak (PLT11).  I was skeptical at first – would it harm my engine? Would it work? I found it easily at my local auto parts store and bought it. It was easy to use, the directions were clear, I applied it and waited . . . then drove. It worked like magic. We got to the hospital without incident, and to be honest, I actually waited a few weeks before I took it in because the product worked so well that it was no longer an emergency. I was floored that it really did what it said it would and did not seem to harm my car at all! Thank you!

 by Steve B.
Fixed leak first time

Had a leak in radiator and Bar's Leaks PLT11 pelletized stop leak product fixed the leak first time. 

Thanks for a great product guys.

 by Chris W.
Works flawlessly

I used Bar’s Leaks Radiator Stop Leak PLT11 on my '71 Mercury Cougar GT. Worked flawlessly as did all the Bar's Leaks products I've used over the years.    

 by Dan C.
Great stuff

My take on Bar's Leaks Pelletized Heavy Duty Stop Leak (PLT11) 🔽

For our old inherited ‘56 Chevy, it stopped the radiator from leaking so the engine would not overheat anymore, like it used to with a slight leak. No worries after using it so we could drive anywhere. Great stuff.

 by Dave M.
Helped me get my family home safely

This review is for Bar’s Leaks Pelletized Radiator Heavy Duty Stop Leak, part #PLT11.

Product came in clutch to save the day when I needed it the most. April 27th ‘95 my son was born. I was heading to the hospital to take him and my wife home. Car cabin of that '83 Mercury Marquis filled with the familiar sweet smell. My heater core sprung a leak. I ran into Pep Boys and picked up a bottle of Bar’s Leaks Pelletized Radiator Heavy Duty Stop Leak poured it in the radiator soon the leak was stopped and I could get my family home safely. 

Product held wonderfully.   I replaced the core two weeks later.

 by Herb M.
Satisfied customer once again!

We are a family that has been in trucking 107 years and have had stints at retail sales as well. Our father had an Esso gas and service station in the 50s when I was a kid, and we sold many products through the years. I don't remember the first we used Bar's Leaks, but we called it the GRAVEL STOP LEAK that worked! 

We have used it in all type vehicles from automobiles to very heavy earthmoving equipment such as HD41 Allis Chalmers bulldozers, and to highway trucks of many brands. I have used the Bar's Leaks Heavy Duty Pelletized stop leak in an English Manufactured Ford Super Major farm tractor which has" Wet sleeve" engine design which had a problem with the rubber cylinder sleeve "O" ring leaking causing coolant to get in the engine lubricating oil. Not a good thing at all!"

I put the Bar's Leaks in the tractor 5 or 6 years ago, it stopped the leak, and has continued to have the leak stopped ever since. Thus, I did not have to tear the engine down to replace the liner seals, saving a tremendous amount of time and money.

We are also in to Antique heavy trucks as members of The Keystone Chapter of The Antique Truck Club of America. Currently, I have a 1972 Mack R795ST truck tractor with the original Mack Maxidyne 325 Horsepower V8 engine with 614,000 miles on it and it has never been torn down for any reason. this also a wet sleeve engine and, fortunately, it has not had any sleeve leakage to date. However, it does have a minor seepage at the lower radiator hose attachment gasket where the adapter bolts to the lower radiator tank. I tried the bolts to remove the adapter and replace the gasket itself, but to no reasonable avail. I am fearful of breaking off the 7/16th inch bolts holding the adapter on and thus require drilling them out of the radiator.

Therefore, I went to the old standby, Bar's Leaks Pelletized Heavy Duty Stop Leak and solved the leak/seepage problem with only one bottle of the stop leak. Satisfied customer once again! 

I am very happy with the product, and in both these cases, completely satisfied, because each of these vehicles, the tractor is a 1957, and the Mack a 1972, are original survivors so I do not want to do any excess repair to them to take away from their originality. 

Bar's Leaks, GOOD STUFF!

Bar's Leaks response: Thanks for your incredibly thoughtful and detailed review, Herb. We are a veteran- and family-owned business that's been in the industry for over 75 years. Many kudos to your 107 year old company. Keep on trucking! 😉

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