ST5516 Heavy-Duty Multi-Purpose One Step Permanent Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required

Vehicle leaking coolant, about 1gal per 1,000 mi driven. Dealer diagnosed as jiffy tight fittings on turbos with a repair estimate of $3,300. 2015 Ford F-150 - 3.5L Ecoboost with 140K miles so didn't want to put that kind of cash into a high mileage vehicle. Added as directed and leaks stopped immediately. 1K miles later, coolant level in the overflow tank has not gone down at all.

Good product

I just concluded a 7,000 mile drive from Georgia to Oklahoma, then to Cali and from there, Washington state and then back to Georgia in my 2002 Chevy Tahoe while hauling a 21' toy hauler heavy laden with toys. My Tahoe has an aftermarket radiator that produced a pinhole leak during travel. I couldn't directly locate the leak nor was I able to just replace the radiator as I was traveling. So I considered using a radiator stop leak but hesitant to do so as I didn't want to plug up my cooling system at all. I found this product and due to the reviews, decided to try it. It worked almost immediately after running the engine for a while to circulate the solution. And it still has not shown signs of leaking and no affect of the cooling capabilities either. I highly recommend this product!

I bought these to use on my 2011 f350 diesel with a leak on one of the front seals behind the water pump, if I wante to fix it right I would have to take the whole front end of my truck, fan, water pump, and even the front crank cover, no way,, so I bough this mainly because the manufacturer stated that this were permanent, not temporaty fixes, so Bought it, pour just half the bottle and wow! it stoppe, I was impress, but then a cold front arrived and neded to use my heater (wich I just replaced last winter with an OEM heater core) and bam!!! mildy warm air was comming out of the vents, so.... I guess i will now have to replace the heater core wich I can do in about 5 hours (take center console out, and then dash and it literally takes less than 5 minutes to take the old heater core out and put the new one in) I guess is better that taking the front end what I would do different now it would be using this product and then cutting my heater core lines and splicing then togheter to bypass my heater core, let this stop leak do the magic and then flush the old coolant, put new one in and then connect back the heater lines

This thing saved me thousands of dollars. I thought of taking the time to write a review because this is the best $20 I have ever spent. I actually used it three times already over the course of 2 years. So yes... over time I think you will need to use it again. In my case it took about 5-7 months before the coolant started leaking badly again. Then I purchased another bottle and it did the job again for my 04 dodge ram 1500. And again for a third time, which I used a month ago. Not only it sealed the leak, again, not 100%, but good enough for the engine light to go off, and i was able to pass inspection twice. Before i used it for the first time, my truck was about to give up after 3 years it was leaking from coolant to engine (mixing with the engine oil). The only solution was a rebuild or get a new engine that would cost over $3500. It is a great product. Not perfect, but if you have an old car with a leaking coolant system, and if don't want to start spending thousands of $, this is the best product you can find (I tried 2 others before this one, and it was not as good).

I can’t say it worked 100%. I was not able to have the product work completely into the system to have it work fully. But it did slow down the leak to where I was only putting 1 gallon of coolant instead of 2 gallons of coolant a day into my truck. I end up getting repairs done sooner than I wanted. One of the seals had a crack in it. That’s why it was leaking coolant into my oil. But the stuff gets all through your system, and I had to flush everything out. It did end up in my oil pan. It did not seem to cause any harm to the system at all. It was easy to pour into the reservoir tank. When you look into the reservoir tank, you can see the small particles of copper. It did not seem to cause my heat level to rise either.

Does not work for over pressurized coolant system caused by exhaust gases getting into the coolant system. Followed the directions to the letter for over pressurization leak but to no avail, K-Seal did not work for my issue.

I waited 5 days to write this review on my birthday. Mainly because I am so impressed with this product and I didn't know that it would hold. I'm not getting paid for this review and I rarely write reviews. A little history. I own a 2007 Mercedes E-63. This car is a beast and is a joy to drive. The dealership diagnosed a blown head gasket on the car. The report shows coolant mixed with the engine oil. My oil almost looked like a mocha espresso. A very bad sign. The car was immediately overheating. I was adding antifreeze every day. The dealership estimated repairs to start at $15K but could easily rise to $25K. Once the top of the motor is opened up I'm sure they would recommend new cams (4), new cam adjusters and of course new seals. A new crate engine for this car from Mercedes-Benz costs $57,000.00. After carefully reading the directions I added coolant with the bottle of K-seal after shaking it for 1 minute. Then I drove the car normally for 20-25 minutes. The car came up to temperature and stayed there. It didn't overheat! After feeling terribly about having to sell the car as a mechanic's special or donating the car I can instead enjoy driving the car daily. I did end up changing the oil 3 times before it didn't appear to have any more coolant in it. Thanks K-seal!