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

Iona 2004 GMC Yukon and it’s been leaking from the radiator from an unknown location for over a year and so I was skeptical. I poured this product in the radiator as instructed and it worked first time. No leak

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.

It worked out fine for me. After a first use, there was still a drop leak from time to time. I reapplied it a second time and it seems it worked out fine this time.

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.

I had a transmission leak from a freeze plug behind the bell housing. This product stopped the leak in 15 minutes with no effort compared to dropping the transmission to replace the freeze plug. Saved me hours of hassle and bloody knuckles. 5 stars.

Bought this product to seal small leak in radiator of my 2012 Jeep Grand Cherokee Overland w/5.7 HEMI V8. Does not work at all, 1 day after adding it to my colling system I was at gas station waiting in line and guy next to me said I'm leaking something under my vehicle. I got out and sure enough, Water from radiator was still leaking from same location as before. Don't waste your money on this product, it isn't worth the money or the headaches. Bars Leak is by far the best radiator sealant on the market and has been for years but i thought I would give this product a try. Should have taken the extra time to drive to auto parts store to pickup Bars leak.

Didn't fix my leak

This product is a life saver. The water pump of my car start to leak heavily, so I pour abottle of k-seal on the radiator and the leak was reduced at 97%. It gave the time to keep runing the car for a couple of weeks until I get the new water pump and installed. Obviously I check the radiator level daily but the product due his work compared to the scale of damage the water pump seal had.

Great product

Seems to stop leaking from plastic header of the radiator.

The best coolant leak repair product available!I have used it many times on leaking radiators and cracked engine blocks.Really good product,does the job every time.

merhaba aracımda 2-3 günde 50-60 km kullanım sonrasında 500 ml kadar ciddi bir su eksiltme problemi vardı 20 şubat günü ürünü kullanım talimatına uygun olarak yedek depo içinde full antifiriz varken kullandım ilk kullanım sonrası 250 ml kadar bir eksiltme yaptı üzerini max çizgisine kadar tekrar antifiriz ile tamamladım 45 gün kadar oldu her hangi bir eksiltme olmadı şu an için daha önce kulladığım bir çok üründen daha başarılı

Ich habe dieses Produkt bereits mehrfach bei verschiedenen Fahrzeugen verwendet. Es hat jedes Mal zuverlässig funktioniert und kleinere Undichtigkeiten im Kühlsystem erfolgreich abgedichtet. Die Anwendung ist einfach und das Produkt hat sich für mich bewährt. Ich bin sehr zufrieden und kann es weiterempfehlen.