K-Seal Reviews 530

TrustScore 4 out of 5

3.8

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Review summary

Created with AI, based on recent reviews

Looking at 23 reviews, reviewers had a great experience with this company. Customers are really happy with the product, often noting its effectiveness in resolving issues like coolant leaks and head gasket problems. Many people mention that the product works quickly, with some seeing improvements within minutes or after a short drive. Reviewers appreciate that the product can fix various types of leaks and that it doesn't leave behind residue or cause clogging in the cooling system. However, some customers were dissatisfied with the product's performance, reporting that it did not fix their leaks or that it caused issues like clogging the coolant system and new thermostats. A few other people also felt that the product was not effective for severe damage or specific types of oil leaks into the coolant system.

What people talk about most

Product

Reviewers mention ambiguous feedback about product. Many customers report that the product successfully fixed... See more

Quality

Customers had ambiguous experiences with quality. Many reviewers reported positive outcomes, with some... See more

Reviews shaping this summary

Rated 3 out of 5 stars

I bought this product a week before Christmas because my car started pressurizing coolant into the overflow bottle and getting hot due to low coolant in the radiator. I never let it boil and had to nu... See more

Company replied

Rated 3 out of 5 stars

First of all. I believe in this product. I went online and read all the usage instructions. I think I have major problems with the head gasket and block after major overheating. This stuff has made... See more

Company replied

Rated 3 out of 5 stars

This is the first part of the review : Today 15/08/2025 I finally managed to buy k seal through Malaysia site and I had to go to get it as it does not sell in thailand . I am looking forwa... See more

Company replied

Rated 5 out of 5 stars

Good product. Worked on a previous car. Recently had a garage put it in my car without warning me. Car is still working but didn't/doesn't have any warning signs of a head gasket. Garage then pro... See more

Company replied


Company details

  1. Car service
  2. Car Radiator Repair Service
  3. Vehicle Repair

Written by the company

K-Seal is the one-step permanent repair for all engine coolant leaks. It could save you thousands in garage fees! K-Seal will permanently repair coolant leaks in the head, head gasket, engine block, radiator, heater core, water pump casing and freeze plug. K-Seal is compatible with all types of anti freeze so there is no need to drain or flush the cooling system. Simply Shake, Pour & Go! With over 12 million bottles sold worldwide K-Seal is the number one bestselling coolant leak repair in the USA and is the choice of leading international roadside recovery organisation to help keep their members on the road. K-Seal has been independently university tested in the United Kingdom to meet ASTM D3147, the coolant leak repair standard. K-Seal is available from all leading auto parts stores and online resellers.

K-Seal Guarantee That a Successful Repair is Permanent.

From a replacement bottle up to a full money back guarantee we have you covered.

From a replacement bottle up to a full money back guarantee we have you covered.
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.

Contact info

3.8

Great

TrustScore 4 out of 5

530 reviews

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Replied to 100% of negative reviews

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Rated 1 out of 5 stars

Poor product, hope did not mess up engine ,asked…


studied different products,asked questions, said it was great product. Did used it in my 2009 Dodge Caravan. Had a small leak since brought it new. Dealer could not locate leak. So put up with it and approx., 6 months ago used it' It worked. About 2 weeks ago had heater problems, felt like thermostat. Open up the hose to remove thermostat, never seen such a mess. orange color. thermostat plugged. still not able to use vehicle.Never put that garbage in any vehicle or would recommend it. I am hoping can get it going. Also had it at garage to clean out and flush!!

26 February 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi LeRoy,

Thank you for the feedback, and although I appreciate you asking questions, I cannot find any email communication with us.

It is essential to understand how K-Seal works because after six months, it will be ineffective and not the cause of any issues you are experiencing.

We would be happy to have the replaced parts examined and share our findings with you and the mechanic you have used for the clean and flush.

I would also appreciate being sent any pictures of what you discovered, and if I have missed any contact with ourselves, I apologise, as I believe we would have been able to help.

Colin.

Rated 5 out of 5 stars

I was very nervous

I was very nervous - I found lots of positive reviews, but also plenty of negative ones. But I realised most of the negative ones were based on opinions rather than experience. I only used it as a last resort, when no leaks could be visually detected. I suspect it was the heater matrix, but wasn't going to invest time checking.
But it's fixed. 10 days later still hasn't moved.

10 February 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Ben,

Thank you for interrogating the positive and negative reviews. In addition to opinions, they are also from people who have never contacted us to seek advice or answers.

I am thrilled we were able to help, and if this was a Heater Matrix issue, we hopefully saved you a lot of money as well.

These can be expensive repairs due to the amount of labour involved.

Colin.

Rated 5 out of 5 stars

Magic in a bottle

A friend pulled up.in his 2011 ford transit t280. Coolant wasn't holding 5 litres just disappear coming out radiator etc. He checked all external.hoses which were tight.

Another friend solved head gasket blown on a merc lasted another 2 years and was still running.

Anyways we put stuff in, within 1 min the leak seem to have stopped. Took I for a good run a little coolant dropped.

Filled it back up no leak was amazed took a fresh 5l coolant hasn't lost nothing. Engine gauge staying on 90c engines not over heating. So far so good.

19 February 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi John,

One of the benefits of K-Seal is that our formula will find any coolant leak due to the pressure differential when the liquid is escaping.

Quite often, a leak is hidden away somewhere, and so long as this is not a rubber hose, we can usually solve the coolant leak quickly.

I love the title of this review, and I should use it in our marketing.

Thank you for the review, and I appreciate the time taken to let others know.

Colin.

Rated 5 out of 5 stars

This product really works

This product really works, I had my doubts but was proved wrong. Saved me $$$$$$$$$$

5 February 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Jim,

Thank you for the review, and looking back at our communications, I am thrilled we were able to help with a replacement bottle that has now been successful.

It is always worth reaching out to us if we have not managed to solve the coolant leak the first time because a follow-up dose of K-Seal might be the answer.

Colin.

Rated 5 out of 5 stars

Fantastic Product

My prior experience with similar products had not been good. I bought them trying to avoid an expensive fix, which I ended up paying for. There are other products that require complicated steps that I couldn’t accomplish. The KSeal just goes into the overflow reservoir and then drive to temperature. And it worked! Since added I haven’t lost a teaspoon of coolant and no more vapor trail on cool mornings. I’m ecstatic.

18 January 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Benjamin,

Thank you so much for the review. We only get a few customers in the U.A.E., so our international sales director will be very pleased.

With the white vapour, I presume you were solving a head gasket coolant leak.

Keep us informed if anything changes.

Colin.

Rated 5 out of 5 stars

Just used a bottle of HD

Just used a bottle of HD! Always the same result and response from truck owner! Coolant absolutely running out of a radiator, due to the part being curbed heavily. Low truck or mental driver!? I like to get as much heat in the Coolant as possible as I was always told it aids repair. No time really on this occasion, just bunged it in the header. Driver looks on with pessimistic grin. About 1 minute in and a wee trickle was left but it soon dried up after another 30s. I always enjoy just sticking a bottle of coppery stuff in and sitting back to keep me in a job one more day! Also watching the disbelief in the onlookers. Sometimes it's not that dramatic but I have never been let down by this sealant. Again there's a limit to its powers, if you attend a breakdown where you have to search for pieces of Coolant system and engine block I'd save the bottle for another day. As for clogging up tight areas, I worked for JCB. The 444 engine, we were told, had so little tolerance for Coolant transfer that any sealant wouldn't be possible. I tried it on a test engine in our workshop and had no issues at all. However, I'm only speaking from personal experience and I went steady as I poured. Anyway I'm a fan and will continue to enjoy using K-Seal. I always recommend it to people in the trade.

18 January 2024
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Andrew,

Wow, thank you for this fantastic review, and I had to smile at the reference to the disbelief of onlookers.

Also, for the recommendation to others, K-Seal is indeed a Trade Trusted product.

It is always satisfying to see the coolant leak repair before your eyes.

Colin

Rated 3 out of 5 stars

I have used this product successfully previously

I have used this product successfully on a previous occasion to plug a leaking radiator on my Vauxhall Zafira with half a bottle. I am now losing coolant and engine oil through a suspected head gasket leak and an additional full bottle has not cured it this time around.

4 December 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Chris,
I would love for you to email me directly to discuss this further, as I have some additional things to try.
These involve using other products we supply, but K-Seal will struggle with the symptoms you describe.
As you will see on our fold-out rear label, we state, "K-Seal is not suitable for coolant to oil, or oil to coolant leaks."
Colin.
cbenzie@kseal.com

Rated 1 out of 5 stars

Used the head gasket sealer bought from…

Used the head gasket sealer bought from a motor factor and it didn't work despite using a qualified mechanic who recommended it

I read the advice on the bottle I went to your website clicking the link got me nowhere as once clicked on the union jack for uk nothing happened
Try it yourself

15 December 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Stephen,

Sorry that K-Seal was unsuccessful, but without any communication from you, I cannot say why or even if we could have made it work with further instructions.

Having our product recommended by a mechanic and following our mechanic's installation process are two different things.

That product has a full money-back guarantee on the instructions, and I'd like to know if you have seen that as you have not applied for the refund.

We have several five-star reviews where our product has not worked, but the customer service has restored their faith when they reach out to us first.

Colin.

Rated 4 out of 5 stars

Manifold gasket

Manifold gasket, 2001 dekota, when I applied it at first it worked for about two weeks, check engine light came on. Took it to the shop they told me it was two gaskets, add another bottle. Check engine went off, haven’t had a problem in about a month now. It works, I’ll keep u updated

1 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Jeremy,

It's an interesting review and a perfect example of where a second treatment can make a difference.

A single bottle is usually required, but we are always on hand to help if a partial repair needs further treatment.

With over a month and no coolant leak, I am confident you will have many more miles of trouble-free motoring. At least as far as losing coolant is concerned.

Colin

Rated 5 out of 5 stars

k-seal ultimate

Originally purchased k-seal ultimate to fix a potential head gasket leak, gave the stuff a chance to work some magic and it improved the Performance and issues with my vehicle, not 100%.

I got in contact with the customer care team, very quick to response and very helpful, quickly sorted me another bottle to hopefully fully fix the problem.

I would recommend this product to anyone who may have a potential head gasket issue before paying out £1000s even as a temporary fix. It has not caused any clogging issues with my car either.

11 December 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Brandon,

I want to thank you for this 5-star review, especially as it highlights our commitment to our K-Seal ULTIMATE Head Gasket repair product.

This product has our highest guarantee, so you could have the replacement bottle you received, or we will even give you a full refund if it does not work.

We pride ourselves on our customer care, and even if the leak is beyond a stop-leak product, we will do our very best.

Colin.

Rated 1 out of 5 stars

Cause Major oil leak?

i was so excited when O Reiley auto store clerk recommend this product. I bought and used it as direct. After use, I could drive my car longer before the temperature gauge raised to Hot. I emailed K Seal and asked how often can I use their product or can I use other head gadket leak repair brand? no response yet. Yesterday I saw a puddle of oil or coolant leak under the car. I thought it was coolant since i just refill it. This morning I brought my car to Honda dealer for airbag service. They told me my 2005 honda civic leaked lot of oil. I brought my car to an independent auto repair, they told me i have a major oil leak and all oiled related gaskets, radiator and water pump need to be replaced and estimated repair cost is between $1000 -$1500. I know my car has head gasket problem and hope K Seal will repair it but now i have $1000+ in repair for oil leak plus $1200 for head gasket repair. I am so sad.

Before using K Seal, my car had no leak. Its temperature gauge raised hot when driving for 15 minutes soI took it to inspect why. Auto repair shop told me head gasket leak.

5 December 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Christine,

I'm sorry to hear you are not happy with your K-Seal experience.

We replied to your original email within the day, and I was copied in on the reply. Please check your spam folder, as sometimes they get stuck there.

The original issue sounds like it was oil-related. I am sure you will have read our instructions: "K-Seal is not suitable for hoses, water to oil or oil to water leaks."

From what the garage has said, an oil stop-leak product would be more suitable than a coolant leak product.

Colin

Rated 4 out of 5 stars

Well...

Well, it works best for small gasket leaks, is my opinion and experience. If you have a larger leak, this just may not be effective and you will know you have deeper mechanical issues seeing when this won't help you much after using it. It is also just a band aid - and not a cure all, so don't think it's actually like having a real "repair".

22 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Anjie,

Thank you for the review of what I assume may have been a partial or temporary fix?

I encourage potential users to contact us so that we can ask specific questions to determine the size of the leak.

Describing a coolant leak as small or large can be almost anything, and getting further information allows me to calculate the flow rate.

We also like to hear where a repair has failed, as we have either a replacement bottle guarantee or money back depending on the version of K-Seal used.

Colin.

Rated 5 out of 5 stars

It really works.

Man I have tried just about every seal and leak fix they have out there for radiator systems and none have ever worked had better results with glitter. But I tried this stuff and OMG it really works and fast too I couldn't believe it how well it does work and I am a mechanic and been doing this work for years and couldn't believe how well it works definitely recommend trying it out. I drive a Nissan frontier 4x4 with the 4.0l motor and it sealed up my heater core perfectly.

7 December 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Chris,

Thank you for taking the time to let us know about the success K-Seal has had with your leaking Heater Core.

As I have discussed before, this can be a costly repair to replace due to the very high labour costs.

You are also correct in that, given the right circumstances, K-Seal can quickly form a seal.

I have every faith you now have a fully working Heater Core for the winter.

Colin.

Rated 4 out of 5 stars

Very good product but

Very good product but, if you know where the problem is change the part,
It was used on a toyota avensis top hose problem. But the problem still needs fixing hose, 70 pounds. Change it there are limits to a product. If you intend to go on a 7,000 miles trip change the part you idiot.

2 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Andrew,

Thank you for what I think is a fair review, given the limitations of what K-Seal can do. As you will have seen on our fold-out instructions on the bottle, "K-Seal is not suitable for hoses."

Also, given the location of this being a top hose, we would have only ever expected a repair if it were possible to be temporary.

Of course, in some instances, a temporary repair is all that is needed to get you home, in an emergency and give you the chance to replace a problem part.

Colin.

Rated 1 out of 5 stars

Was recommended k seal after developing…

Was recommended k seal after developing a coolant leak. Used as directed and then heating stopped working. Took it to garage who said although it had sealed the leak in the coolant tank it had also blocked other places in the cooling system, it's now going to cost me 200 pound to have the entire system flushed to get rid of the kseal out of it (if that works 🤞) moral of the story - go to a reputable garage and let them fix the problem (which would have prob been not much more that I paid for k seal and 2 bottles of coolant) and avoid further more expensive issue's

29 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Amanda,
I am very sorry you have had an unsatisfactory experience using K-Seal. It is difficult for me to comment as you have never contacted us.
Receiving the mechanics' report on what he believes K-Seal has done will be of great interest.
I can then contact them to advise on possible root causes that are not K-Seal related.

Colin.

Rated 5 out of 5 stars

This product is awesome it saved me a…

This product is awesome it saved me a lot of work from replacing my heater core I got one bottle and the crack was too big and they sent me a replacement one and it sealed it all the way up they back up their guarantee and everything it's definitely worth buying

10 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Jeffery,

It's great to hear we have been successful with this Heater Core coolant leak. Due to the amount of man-hours involved in this repair, it can be very costly.

Also, it will be of great interest to readers of this review to know that contacting us and allowing us to help can yield favourable results rather than just offering a negative review.

Colin.

Rated 5 out of 5 stars

My 1997 BMW Z3 Roadster was losing…

My 1997 BMW Z3 Roadster was losing about 1 ounce of coolant every 300 miles. I couldn't find the leak. At the repair shop they found the radiator had small leaks. This is not unusual for this model BMW. They replaced the radiator and pressure tested the system. They assured me it was corrected. However, the car continued to lose coolant at the same rate. I had the car pressured tested again. No leaks detected. I added K Seal per the instructions. The car has not been losing any coolant for about two weeks and over 400 miles of travel. I'm keeping my fingers crossed that the K Seal will not damage any other parts, as I had recently installed a new water pump, thermostat and radiator hoses.

8 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Bruce,

Thank you for this, and a typical example, I am afraid that a mechanical repair did not find the root cause.

The benefit of K-Seal is that it will be drawn out of the coolant wherever there is a pressure differential, which can typically be hidden from view.

Four hundred miles since then is a good start, and I am confident we have solved the leak. Do not forget we are here should the situation change with our replacement bottle guarantee.

Colin.

Rated 3 out of 5 stars

Right out of the blue I had the low…

Right out of the blue I had the low coolant warning light come on with my BMW X1. I pulled over to check this out and saw was a pretty good sized puddle under the car. I pulled into the next parking spot and within a minute I had another puddle, a big leak indeed.

I was only about 3 miles from home so I got a delivery service to bring my a bottle of pre-mix and filled it up, I had to stop halfway when the coolant light came on to top it off again and the light came on again as I’m pulling in, it saved me a tow but this was really spewing out and had used almost the whole bottle go drive 3 miles.

Just from the way it spewed out while driving and where the leak was, where the water pump is, I figured that was it, and when I took it in to the repair shop which is luckily only half a block away they told me the water pump has to go. I had ordered a bottle of K-Seal the night before and the garage told e to come back in 3 weeks because they are all booked up, so I started thinking of using this to get by until then perhaps and still let me drive my car.

I did a lot of research on this and in the end I decided against it and wanted to explain why. I’m going to say that there may be a time and place for this stuff but this is more like a Hail Mary pass and even though the repair will cost me $1600 CDN I’m not really going to be able to avoid this nor do I really want to.

Water pump coolant leaks are pretty challenging as this is a moving part but there is also the concern that the pump may have and probably has failed and if you slow down or stop the leak the damage that caused it may not allow the pump to do its vital job, leading to much worse consequences.

Still though, I at least considered putting this in anyway as it is going to cost me a fair bit of money in taxi fares while I wait for them to fix this, which I then weighed against the risks.

I read every post on this site and also looked elsewhere and while it may be assuring that the particles are small enough to pass through, an uncomfortably high number of users reported this clogging up their rads and heater cores and the stuff seems to have a tendency to coagulate in at least some cases, perhaps being exposed to higher than normal amounts of heat, and I never drive more than 5 miles at a time so while I barely get the thing up to operating temperature, this process was.still too much of an unknown to risk doubling my repair bill or worse, People have found pea sized clumps of this in their coolant systems, and telling us that each particle is too small is of no solace if enough of them clump together to form clogs.

Still though, I understand that if you can’t afford to fix your car or it doesn’t make sense to then throwing the Hail Mary may be the only good option. I’m actually keeping the stuff in case I ever get to this point and this is surely the only product I would ever use if it ever gets to that.

I wanted to share this to emphasize how important it is to think these things through even though k-seal is dirt cheap and only cost me $32 to have this on hand. I would have liked to see the company address the concern of clogging though beyond just saying the particles themselves are too small, and perhaps better advise on which situations may elevate this risk, rather than just going into denial every time. This does not bring comfort to those who are concerned about such things.

12 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi A.J.

That is undoubtedly a well-thought-out and concise reply I will keep for others to read even though you have not used the product.

Hopefully, you may feel inclined to up this to a 4-Star as I am going to wholeheartedly address your misconception that we only state that our particles are too small to cause any damage.

K-Seal conforms to the US ASTM D-3147 standard for coolant leak products, ensuring scientifically what we can and cannot do.

We even have a dedicated webpage outlining this research:
https://www.kseal.com/using-k-seal/how-does-k-seal-work/scientifically-tested

If anyone would like further information on this, I would be more than happy to provide further written testing evidence c.benzie@kseal.com

I am confident that I could combat your findings of "People have found pea sized clumps" because, in over ten years of managing K-Seal technical enquiries, I have yet to be shown a single picture of this.

Colin.

Rated 4 out of 5 stars

Hi guys this was recommended by so…

Hi guys this was recommended by so many friends. I have Toyota Sienna 2014 only driven 130K and it has minor leak (like 200 ML for every 400KM). ordered this already. wondering how to add(coolant reservoir ?) I have to wait until this goes down?

15 November 2023
Unprompted review
K-Seal logo

Reply from K-Seal

Hi Kokulan,
Thank you for the question, and I would love to discuss this further with you.
Her is not the place for a technical discussion so please email me cbenzie@kseal.com
I can then ask specific questions, based on your particular symptoms. Colin.

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