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If you use ULTIMATE for a Head Gasket repair and it and it fails to fix the leak get in touch to find out about our money back guarantee. For all our other brands if you have a repair that subsequently fails contact us for a replacement bottle.
Reviews 493
hugh costello
Jan 29,2025I bought the small bottle of K seal as I was topping my radiator fluid every 2 weeks especially after a longish drive around 80 miles each way. I didn't expect too much. BUT IT WORKED GREAT. been in around 4 months no more topping up coolant. I wasn't losing coolant from radiator but I was losing it from somewhere give it a try nothing to lose ☺️
Business user
Jan 21,2025Excellent advice from Mike as I was unsure if KSeal would be compatible in a big 4L V8 performance vehicle. It worked!! An absolutely amazing outcome. So happy the big car is holding water now!!!
Dumpling Central
Jan 14,2025Very disappointed. Called them a week ago and they assured me they would get right back to me the following day with some kind of solution, understanding the dire urgency of my situation. No one called me back, so I had to just phone them again today, twice, and they are putting me off saying they will get back to me, again. Really? When?! Perhaps this honest review might get their attention. Used a half bottle of K Seal based on the recommendation of a mechanic as I could not afford a costly coolant repair, and it has ruined my car. My PSM failure light now comes on intermittently as well as the full time warning engine light being on, and my kids and I are now stranded here way out in the country where we live, an hour form the city. This is my only vehicle, and is now not drivable, and I cannot take myself to breast cancer treatments nor take my kids to swim practice, or even get to the grocery store. Thanks to this product, my situation has gone from bad to worse, and I hope they will take responsibility and pay to get my system thoroughly flushed out as I cannot afford to do so. I have since spoken to numerous mechanics as well as my local Porsche dealer and they said to never, ever use this product as it damages the system it is supposed to repair, resulting in sensor damage, clogging up the system, etc, etc...they actually warn people to never use this product and most say that they will not service any vehicle that has K Seal in it due to the numerous, mostly unfixable issues it causes to high performance cars. I am so distraught over this, I have lost sleep because I am in a dire situation without my vehicle and no money to cover what sounds like a costly and lengthy repair situation. And for history on the vehicle...I am the one and only owner of this vehicle and have maintained it perfectly for the past 18 years, and up until today it has never had any major issues. It only needed the occasional brakes, tires, oil changes, annual service, etc....so I know the complete history of my vehicle and have been the sole owner. It has been a faithful, reliable car without any major issues. And to make matters worse, the one woman who answered the phone today was aloof, dismissive, and unkind, saying there was nothing she can do about anything and I will just have to wait for them to get back to me. Seriously? RUDE!! Please K Seal, do the right thing and help me get my car flushed and drivable! How could you do this to an innocent customer?
Dave Gipps
Jan 02,2025Never let me down . Gone are the bad old days of radweld 40 yrs ago blocking pipes . K-seal has been excellent for me and always carry a spare bottle.
chuck palmer
Jan 02,2025I put K-Seal in my old pickup about 18 months ago and it did not work, but I chalked it up to all the junk that was in my radiator (including B...D....) fluid that had not been changed for probably 10 years. I drained the radiator, put in new antifreeze and topped it off with another bottle of K-Seal Ultimate. Instant success and I have been driving on it for almost 2 years. Couldn't be happier for what I think will be a permanent fix.
KW
Dec 21,2024Unfortunately it did not work in my case however they did honor their refund. Thank you so much. Great customer service.
Greg Fujii
Dec 19,2024I tried it twice on my Subaru and didn't work
Johnny Lucas
Dec 13,2024K-Seal clogged my heater core, which cost me hundreds of dollars and dozens of hours to get it all out of the system so I could have working heat again. K-Seal says, "The particles in our K-Seal products are very precisely designed to be large enough to repair holes up to 0.635mm in size but deliberately small enough to never block any passageways or tubes within the cooling system, including those inside the heater core and radiator." This is absolutely false. It did stop the leak as intended, but the particles were not small enough to pass through the heater core without clogging it up.
J C
Dec 13,2024I have a 2004 Jaguar xtype that had a "mystery" coolant leak. I was told that all hoses and clamps needed to be replaced. Instead I used K-Seal once and the leak stopped immediately. What a great product!
Mitch Baldwin
Nov 22,2024Did my due diligence... I have an Audi A3 Quattro 2015 and had a very minor leak from the water pump.Thermostat area, only required top-up every 4 weeks, but annoying as puddles after cold sitting, so thinking it was an expansion sealing leak. I looked at doing it myself to replace the gaskets and is a massive job 14 hrs +... (I'm a caravan mechanic so have all the tools and able to do repairs) So when researching I came across K-seal and read like 200 reviews and took the line, if it doesn't work ill have to replace coolant anyway... As my leak was very minor I decided to add 1/3rd of a bottle and see what happened... So as instructed I added the liquid and ran the engine for 20 mins at idle. The leak has now gone and not a drop since, so my thoughts are the small gasket leak was plugged easily and no leaks in the last few days.. all dry . I will probably flush the coolant in a week so its back to usual. I had a look at the cost to replace the water pump and gaskets and would have been $1000 (AUD) or more depending on what needed doing, so I'm happy its fixed the leak and saved me a hefty sum. I'm aware it may need doing eventually but at this point I'm stoked it repaired the small leak with only a 3rd of a bottle... So yes it works..
Terry Mathews
Nov 21,2024Great product and easy to use. Saved me so much time and money and no predatory repair people. I figured I had nothing to lose but a old van with over 250000 miles
ARNOLD
Nov 13,2024I bought the product yesterday for $30.00. I added it directly to the radiator, and I then ran the vehicle for about 20 minutes longer than the time suggested on the bottle. At first, it seemed like it might be working, it never was able to completely seal the head gasket leak. On the bottle it said that it is 100% guaranteed or your money back. I'm hoping I am able to get my money back. It would probably work for smaller head gasket leaks, but apparently the head gasket on my 2010 pontiac vibe 1.8l has to large of a leak.
David Renfrow
Nov 08,2024Amazing product! Out of state, on a trip, 30 minutes before a shop closed for the day, I had a major coolant leak. Possibly the water pump housing. A mechanic added K Seal, and told me, he had seen it do things he never thought possible. I laughed at him. No way this is going to stop that leak. I guess he's laughing now. It not only stopped it, I can't find where it was leaking. I don't know how it works, but I do know it works. I had never heard of this brand before, but I tell everyone about it now. Keep some with you, because you never know when you may need it.
Roman Florea
Oct 30,2024Don't use this f.....g product will destroy your engine and coolant system i use on my car and i think my system it's blocked now do a lot of pressure in coolant tank all hose it's very hard and engine only like 1min work after stop alone now need to sell my car on scrap from fould of k-seal
Anita
Oct 24,2024All I can say is WOW! I am still shocked that this K-Seal ultimate actually took care of my head gasket leak in my 2011 Toyota RAV 4! I had 2 garages tell me I needed a new Engine and one shop quoted me $3,700 to replace the head gasket. Mind you, my engine only has 99,000 miles on it. Figured it was worth a shot to try K-Seal. Turned out to be the best 28 bucks I’ve ever spent!!
rob stehouwer
Oct 21,2024Ik heb 2 flesjes k-seal in de radiator gedaan omdat deze lek was en het heeft 3 weken het lek dicht gehouden. Er staat permanent op en dat vind ik niet ik ben teleur gesteld.
Carl lindsay
Oct 17,2024I followed the direction in installing this k-seal head gasket repair. I have a 4.3 vortec engine. I drove the van hot. I decided to give k-seal a try. I also gave blue devil a try. Both only work up to 90%. I still got coolent in my oil plus I still had a miss fire. I took the cylinder heads off. The passage head was cracked.it may of worked if it was a blown head gasket.carl
Elyissa Ella
Oct 16,2024Shocking I called AA as I had a possible coolant leak but they couldn't tell much because it was raining how ever the coolant was below minmin so most likely coolant leak anways they said they can put some k seal init said everything with car will be OK 45mins later no leaks but car blowing cold air and car fan keeps cutting out this is now gonna cost us so much more money this needs taken of the shelfs costing people money il be sueing your company but also AA aswell
Kevin blanks
Oct 15,20242 bottles for a pinhole didn't work slowed but didn't seal the leak
Michael Langstaff
Feb 24,2025Do not use K-Seal. It blocked up the heater matrix pipes in my car and the car overheated within a few minutes of starting up. Before that the car was driving fine but no heat coming from the heaters 30 mph and under. Only heat coming out at 50 mph and over. This is because the K-Seal was blocking the heater matrix pipes. I had to have the car recovered and repaired at a garage. The garage confirmed it was the result of using K-Seal. Yes the product will fix your car and stop leaks temporarily. However, in the long term it will damage your car and cause more problems. K-Seal after a few months of being in the coolant system turns into a muddy/sandy type residue that blocks everything up in your car's cooling system. You have been warned.