K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, 8oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required

I have a 2000 Pontiac Grand AM GT V6 3400 engine, bought the car new from the dealer. A few years back the engine developed a coolant leak in the lower intake manifold, discovered oil in the coolant and needed to fill the radiator tank every couple of weeks. I had a mechanic remove the intake and replace the gaskets; he also suggest I have the heads removed and new head gaskets installed while he had it apart. $1,500 later it was back together and running great, no more leaks. Fast forward about 10K miles and a little over a year later, out of warranty I may add, the engine would smell of coolant and started to leak externally. I was going through a gallon a coolant every couple weeks. Take into account this car has about 100K miles and has a market value of about $1,800. I wasn't going to throw anymore money after bad. So I kept driving it, but one morning I started it up cold and the engine began to miss on 1 or 2 cylinders, the check engine was flashing, indicated the misfiring cylinders. I towed it to another mechanic to see what the cause was, turns out the head gasket was blown this time, compression test proved his theory, he suggested I get another engine from a junked used car and try my luck. That would cost about $3,000 with parts and labor. Not about to throw any more money away, I had the car towed back to my house where it sat for a few months. Not sure what to do with this car, body, paint and interior was in excellent condition, oil was always changed with Mobile 1, it was a well maintained car, was a shame to see it there dead in the driveway. Just had new tires and brakes installed prior to the coolant leak. One day I ran across an article promoting K-Seal, after reading the great reviews here on Amazon, I figured what the heck. It was either call the junk yard and have them pick up the car or spend less than the cost of lunch and give it a shot. Can't believe how easy it was to do, I pulled the radiator hose from the engine block, poured in the K-Seal and reinstalled the hose. The directions state you do not have to drain the coolant like other brands require. Started the car up, and of course the engine was misfiring and check engine light began to flash like before. I let it idle for a few minutes to warm up, when it got to operating temperature, I took it for a drive around the neighborhood. Within about a mile of driving, the engine smoothed out and the CE light went dark. Drove around for another 20 minutes and returned home. I parked the car and check underneath to see if the coolant was leaking like before, to my surprise it had stopped! I let the engine cool and topped off the coolant reservoir with fresh antifreeze until full. I decide to drive the car to work the next day, a 35 miles commute one way into the city, in the middle of summer, ran flawless. Wow! Absolutely no problems since the K-Seal treatment. I have been driving the car now for 7 months and about 6K miles. The coolant hasn't leak a bit and the car runs flawless.Even my mechanic can't believe this stuff actually worked. I am a believer and have since told many people of my experience with this product. Had a buddy with a similar issue with his beloved 2 DR Accord V6, fixed his leak too! I normally don't spend the time to write reviews, but this product truly has made a believer out of me. What do you have to lose? I almost threw away my car, and for a measly few dollars it is now back on the road better than ever. Thank you K-Seal ! I want to add that after reading the one star reviews on this forum that these people were not using the product as intended. It is designed to very small leaks like in gaskets and cracks in the engine block of heads. It needs high heat to cure the fine copper powder that forms a new gasket. If you have a large leak in a radiator, heater core or hose, it's probably not going to work for very long if at all, better off replacing them. Now head gaskets, yes give it a shot! UPDATE: 9/9/16 Still no leaks, I've clocked 20K+ miles on K-Seal with no issues. Hoping for another 20K... buy this stuff. UPDATE: 1/11/17 Well, the engine miss has returned, anti-freeze is disappearing again, head gasket is leaking again. Just poured another bottle of K-Seal in again, within 5 minutes the leak is repaired again. This stuff is great, my old beater is good for another 20K I hope. Money saved again! My mileage on the first repair was 23K miles, not bad for a $11 fix.

Wow my truck was dripping coolant from the back of the engine, totally inaccessible and this just instantly stopped the leak. Worked like magic.

I had a little pin hole leak in my radiator on my 2002 VW Passat wagon (130k miles). It was somewhere in the fins so it wasn't something I could do a JB weld fix on. While i was contemplating spending the six hundred bucks in [parts and labor to replace the radiator, i just kept adding more coolant. It wasn't a really bad leak. Mostly just annoying because of the smell of burning radiator fluid. But after about a week, it just stopped leaking on it's own, so I've been driving around town with my fingers crossed hoping it would not start leaking again. But then we had planned a family trip out to New Mexico from KC. It was about 110 degrees F out and 1,400 miles to cover round trip with very long stretches of highway cutting thought the middle of nowhere, with absolutely nothing around for miles, so the idea that the radiator would probably choose this time to start leaking again was a serious concern to me. Yes, technically I should have just replaced the radiator, but instead i decided to just bring a couple of gallons of pre-mixed coolant along and ordered a bottle of K-Seal to take along as a "just in case" precaution. Sure enough about half way out there the radiator started to leak again. This time worse than before. So i carefully followed the directions, shaking the bottle of K-Seal but poured only about half of the bottle into the reservoir/overflow tank (the bottle said it would treat up to 10 cylinders and worked on cracked cylinder heads and engine blocks, so i figured half a bottle would be plenty for a little radiator pinhole) As other reviewers have observed it does come out as a thickish ugly brown liquid that just sits there in the bottom of your overflow tank. Which is admittedly kind of scary, especially if you are skeptical of these products to begin with. But shortly after the car was up to temperature, the leak stopped, as advertised -- even though the k-seal was still very noticeably sitting at the bottom of the overflow tank. VW antifreeze is reddish pink and the K-seal at the bottom was a darker brown. After driving the rest of the way out there it had mixed with the rest of the coolant so it didn't look as nasty in the tank. I've driven another 1600 miles on it and not had any issues. I think the biggest fear with these types of "sealer" products is not that they will not actually seal the leak, but that they will gum up all the intricate little passageways in your heater core, and the rest of your cooling system, but I haven't had any issues at all with this. If I do, I'll be sure to post back and downgrade my 5-star rating. So, I'm sold. this stuff saved my butt and I would definitely recommend it -- especially if you're in a bind. I would never use this (or any other product like this) as a preventative measure like some of the product testimonials on the K-Seal web site, but if you have an older car that you don't want to dump a bunch of money in for repairs, I'd definitely give this a go.

I am always reluctant to use these kind of products but I thought " hey, it's 2023, automotive chemistry advanced since stop leak fluids used to clog heater cores and water pumps". My issue with the car was a small pinhole leak in the heater core. Since taking apart the dashboard didn't sound fun, against the advice of all my friends, I've decided to use K-Seal. I used it just as it was recommended, turn heat to ON and drove it 20 miles each way. The putrid smell of coolant slowly dissipated inside the vehicle, hence I knew it's working. Second day, I took the car on a short run and guess what? Overheating. Noooooo. Impossible. Stop leak products never do that...well I did some Google searches...yes, they do that occasionally. I think right now the stop seal product clogged the thermostat. The car is good for about 4-5 miles then it starts overheating. I called the K-Seal customer service and a lady answered immediately ( by that I mean after second ring, no wait, no "press 1 for product help"). I told her the story and she said " it's very strange, never happens". Hmm..really? She advised to flush the system and take it from there. I just hope to Jesus, the radiator passages are not clogged. So, I'll give it two stars because I believe that the product did seal the pinhole in the heater core. Unfortunately, it sealed other parts of the cooling system that didn't need sealing, such as ( best case scenario) the thermostat. December 18 follow up. At the advice of KSeal customer service and because the car was overheating, I've dumped the coolant and KSeal and flushed the whole system. I flushed with distilled water and even drove it for 20 min. As soon as I dumped the KSeal, the car started working normally. No more overheating. I dumped the the distilled water and filled with 50/50 generic coolant. No more issues with overheating....but heater core is leaking...again. So in conclusion, I wouldn't bother with this. Like many others said...fix the issue don't bother with K seal. Best case scenario, you can buy time. My case? Not that it didn't even work...it overheated my car and had to spend extra time and money to flush the system to get it out. December 28 Follow Up. So, a few days before Christmas, I called the company again and the same nice lady answered immediately. I told her I flushed the system and now leaks came back with vengeance. She was still at a loss for words but said she will send another bottle for free. In the meantime, I thought about it long and hard, went back to the website and read directions again. I also realized that when I added K The first time, as per instructions, I added to expansion tank. Expansion tank had plenty coolant in it...but the radiator did not. Because my radiator cap was slowly falling apart, the system wasn't pressurizing properly and coolant wasn't really being drawn into the radiator. I was driving with 50% coolant and K Seal couldn't do it's job since not much was taken from the expansion tank. Yesterday, December 27, the second bottle of K Seal arrived. This time, I got my magic funnel which burps the system and in a coolant jug, I mixed the K Seal along with 50-50 coolant. Turned the engine on, funnel attached/installed on the radiator and heat inside the car, to maximum hot. I would like to mention that at this point, most of the coolant from the radiator was leaked out. The car slowly started taking the mixture in and burping air. After about 10 min, the air was not too hot out of the vents, but the fan was on. I went inside the car and gave it a bit of gas. With a big burp of air, more coolant went in and air become super hot in the cab. I kept the engine running with the heat on for about 40 minutes overall. I turned the engine off, took down the funnel and attachments and installed my new radiator cap. Ran the engine again for about 20 min this time to pressurize the leak. Two hours later, I took the cap off and fluid was right at the neck where it should be. Next day, the same thing. I am 98% sure that the leak was fixed. Will check again in a few days. My advice is to add K Seal directly to the radiator if possible. If you have a leak in the system, radiator should be low already. As per instructions, they don't want the K Seal to touch the metal inside the radiator directly so I would mix it in a smaller bottle with some coolant premix or distilled water and then add that directly in the radiator. I would strongly advise using a burping funnel because of air gets into the system, K seal won't work properly. April 2004 update. Heater core started to leak again. K Seal does give you enough time to get to the mechanic though but I would just use it for that. Not as a permanent solution. I bought a heater delete kit and finally took care of the problem. Two weeks later car started to overheat slightly in turn affecting the AC operation. Fluid level seemed ok but coolant was boiling over. Bought a new thermostat and replaced the old one. Did the K Seal clogged it? I don't know, but thermostat was about 7-8 years old and wasn't OEM. Would I use ANY stop leak again? Only if I am broken down on the side of the road.

It has worked for me so far (3000+ miles). I had a moderate sized coolant leak in my 2016 Cadillac ATS 2.0 turbo with 137,000 miles. I was getting rough running on cold start, white smoke during start up and needing to refill the coolant every 200 miles or so. Also getting misfire codes due to coolant in the cylinder. I diverted slightly from the directions. Instead of pouring this directly into the reservoir, I first diluted this 8 oz bottle with 8 oz of 50/50 dexcool coolant. Then started the car, poured in the 16 OZ into the reservoir, and let it run for about 15 min and drove it normally for about 10 min. Then parked it. That was it. The next day, no white smoke, no rough start, and no codes. The car has been running great now for 3 months and over 3000 miles. I did not drain and flush afterwards, I just keep the mix in the system and it is running great. I plan to just keep driving it.

I have a 25 year old Nissan Pathfinder SUV with over 180000 miles that still runs like it did when I drove it off the dealer lot. Last year, it developed a small coolant leak at a connection to a coolant line between the engine and the firewall. The only way to find it was with a coolant system pressure tester. Getting to that connection to replace the hose requires taking off almost everything above the cylinder heads on the engine--many thousands of dollars if I paid a mechanic, days of difficult work for me, or time to sell for most people. I really didn't have anything to lose giving this stuff a try. And it worked! It stopped the leak with no discernable affect on my cooling system or engine. I am writing this review one year later, and the leak is still sealed. No loss of coolant since, and the engine runs at the same operating temp as it always has. Thank you K-Seal!

Can’t beat this price at any supplier or store. Wish it came in larger quantity and leaked a small amount during shipping. Product worked for about 6 months before more was needed to be added so I wouldn’t say it’s permanent but I think this would depend on what product material the leak is in.

I didn't think it worked until I used it I had a 2014 Chevrolet Cruze which after 4 months of purchase (already used) I started to liquefy the refrigerant, I tried several products but they recommend this one and I bought it, I don't know if it was magic but in less than 24 hours there was no liquefaction. It is very easy to use and explains the correct use when putting it into practice. You don't have to disassemble or get too complicated, it's just pouring the contents into the car's coolant tank and that's it. I explain, do not think that if you have a lychee of a hole at first glance it will be sealed, we are talking that this product is for a small sink, a small crack or for some small joint that is defective in the refrigerant system, but if you have a gap or a split pipe or with a large crack, this product is good but it will not make magic. It worked for me, I hope, and for you too.