Pelletized Heavy Duty Stop Leak (PLT11)

Pelletized Heavy Duty Stop Leak


  20 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

  20 Reviews
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 20 reviews
 by Tim M.
Sealed to perfection

The back story in 1975 is interesting at how good the pellets were. I was installing a 7" hood scoop over my 440 6-Pack in a 69 Dodge Super Bee. My Mom was on her deathbed (no sympathy, a lifetime ago) and I was trying to keep my mind off of it as a 19 yr old. In my preoccupied mind I drilled through the hood and right through the top tank of the radiator. A drill bit sized hole. Being a kid supporting a 6 mile per gallon hot rod I didn't have spare money for a tank repair. So I used your product and it sealed it completely. 2 years later when I was moving to CA I sold it and it was still holding. A hot running car and it sealed to perfection. I have told that story many times as I suggest it to people over the years. Love it.

 by D. C. Sr. - Hayward

I wanted to write and let you all know that I am so very happy that your product is one that works I only wish that I would have trusted in this process a little while sooner. My wife's van developed a leak that came from the underside of the rear of her engine. After careful inspection by both me and a local repair shop, it was thought that either the intake gasket had failed or the head gasket. I spent two and a half days breaking the entire engine apart and replacing the intake gaskets and putting it all together just to once again see the leak when I was all complete. As frustrated as I was, I went to the local parts store and shared my frustration. They recommended Bar's Leaks Radiator Heavy Duty Stop Leak. To be honest, I wasn't much of a fan of those stop leak products but I sure didn't want to spend another $300-$400 on replacing the head gaskets and the intake gaskets (of which I just replaced hoping it was the least of the two projects). I bought a jug of your product serial number 046087000472 and within 20 minutes of running the car, THE LEAK WAS GONE!!! I can't believe it!

It has been almost 4 months since I did this weekend project and still no leak! I just wanted to let you all know that you have changed my thinking about Bar's Pelletized Stop Leak. I will recommend your product to anyone who has a leak, before they repeat what I did and spend all that money on a wasted weekend of frustration. Thank you!

 by Steve H. - Des Moines, IA

I am an ASE Master Technician and have 25 years of experience. Recently my work truck ('99 Ford Ranger 4x4 3.0) developed a severe coolant leak from a failed timing cover gasket (quite common on the 3.0 "Vulcan" OHV engines). I was a long ways from the shop and it was around 15 degrees out (not warm enough to work outside in my book). Filling the cooling system with coolant took about 5 minutes before the coolant was too low to circulate. I have never been one to use a stop leak product before, but I decided to give it a try. Im glad I did. Stopped up the leak like magic. Worked so well that i haven't had to repair it yet (a month so far). Heat and cooling system still working just fine. Thanks for a great product that delivers!

 by M. L. - Pleasanton, CA

I guess this is not a question really, but a testimonial. I work in the fast lube industry, and deal with additives every day. When I had vapor and fog coming out of my vents in my '96 F350 with a Powerstroke Diesel, my heart sank, having replaced it less than 6 months ago with a new core.

I will admit, when the idea of radiator stop leak products came to mind, I doubted it would work. I don't really believe in pour in fix-alls just because of the additives I sell, I don't really believe in. I went out on a limb and got a bottle of Pelletized Stop Leak and poured it in the top hose, after dissolving the pellets in hot water. I poured it in and didn't expect anything to happen. Drove it for 5 minutes, and my windows were fogged up. I cleaned the windows and kept driving. Only a little fogging, and after 20 minutes it was done. Fixed! I couldn't believe it.

I would definitely recommend this to anyone I know. I remain skeptical of other "rebuilds in a bottle" but I would sure buy Bar's Leaks again. Bar's, thank you for making a great product that actually works. Feel free to post this as a testimonial. Love the product!

 by K. B. - Newnan

I used The Radiator Heavy Duty Stop Leak in my 96 Acura TL 2.5 five cylinder car with 220,000 miles. I don't have a temp gauge that goes past the midway point anymore. The cooling fan doesn't kick on anymore. I don't have white smoke coming from the hood area anymore. The product did what it is supposed to do -- it sealed up an internal leak in my cooling system my eyes could not see. I will be checking into some of your other products, if and when the time comes. Thanks for putting out a product that WORKS.

 by S. T. - Los Angeles, CA

The heater core in my GMC truck was leaking steam from a tiny crack. Required removal of entire dashboard to repair -- either a $600 job at a shop or two days laying on my back in the truck trying to do it myself. Tried the Alumaseal brand, it didn't work.

With little hope left, I bought an 11 oz bottle of Bars Heavy Duty Stop Leak, poured it in, and started driving the truck around on errands. About 45 minutes later, the steam coming out of my heater vents suddenly stopped and the smell of anti-freeze vanished. The leak was fixed and has stayed that way since. Thanks for saving me $600, Bar's!

 by G. G. - Easton

I used the PLT11, Heavy Duty Radiator Stop Leak. I own a 1991 Nissan Maxima with 95,000 miles on it and for the past few months it started to leak coolant. I think it was in the water pump seal area or even the heater core, anyway I added the radiator formula and not only did it stop the leak, the heater works like it did when new. Thanks.

 by J. G. - Louisville, KY

Over six months ago our 1995 Chevy Lumina (70k miles) started leaking from the radiator. I put in Bar's pellets and no more leak. I also started using Bar's Rear Main Seal leak stopper at every oil change in my 1995 Pontiac Grand Prix (200k miles)and it has drastically decreased my oil leak. Here is the one that blows me away though. That same Grand Prix developed a bad radiator leak about 3 wks. ago. I put Bar's pellets in and the leak stopped. For a few days that is. The leak came back again and then stopped again. This proceeded for about three weeks. But my car never ran hot. Finally, I replaced the radiator this past weekend and to my surprise there was a 3inch crack in the plastic tank on the drivers side of the radiator. The crack had even started to spread apart. It was very easy to locate once the radiator was out of the car. I was amazed that the Bar's product kept filling in the crack and allowing me to continue driving. I am telling everyone about it. This product is amazing.

 by C. H. Catasauqua - Pittsburgh, PA

Your testimonial pages are no joke! Wow!

I have always been leery about adding anything at all to the coolant systems in my cars over the years. But this time, facing a major repair bill, I decided I have nothing to lose other than about five dollars. I drive a 1996 Monte Carlo 3.1 V6 (which by the way has been notorious for having lower intake manifold leaks) the low coolant light came on a few weeks ago. In a matter of a few miles after that, I was burning coolant in my exhaust and it was leaking out of the intake, spraying onto my serpentine belt and basically making a mess in the engine compartment. I talked to a few of the guys I work with (old-timers) and they recommended using Bar's Leaks. I was definitely hesitant, but trusted their judgment. The next day I bought the pellets, used it accordingly, and in amazement, I have driven about 5,000 miles since, with no leaks, no squealing, and no mess. The engine runs smooth, quiet, no smells and best of all, doesn'’t over-heat! While I'm sure your product won't fix everything, it definitely fixes those nuisance problems. It saved me almost $700 in repairs, and for that, I thank you very much.

 by Roy R. - San Antonio, TX

I own a 1999 Chevy Suburban and a 1992 Pontiac Bonneville. Both cars are daily drivers and have used your fine products now for five years. Bar's Pelletized Stop Leak is without a doubt the finest product on the market. It simply yet elegantly works and does what it promises. Both cars had leaks and one treatment with your Bar's stopped all leaks within twenty four hours, outstanding performance and value and overall a very solid product. Well done and many thanks and my personal wishes for a safe and happy new year!

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