20 Best Engine Coolant Stop Leak (2023 Updated)

Awesome product. My TJ Jeep Wrangler started leaking it’s anti-freeze and couldn’t find the leak. To ease my mind while driving and avoid getting stuck out on a road with a “steaming” radiator, I poured Bar’s Leaks Liquid Aluminum Radiator and Heater Core Stop Leak.

The product started right away and I could see that no leaks after driving around with the solution inside my radiator. There was a “funky” smell for a couple of minutes but I am guessing its either the surrounding area (have my windows open) or from the product.

Either way, the smell dissipated after a few minutes. Jeep’s running well and smoothly again. I might replaced the radiator and replace the hoses too, Meanwhile, the Bar’s Leaks Liquid Aluminum Radiator and Heater Core Stop Leak, is still providing solid performance on a very hard working Jeep engine.

I tried this plus Jb weld radiator repair kit. My oem honda radiator lasted 300k. After spending lots of money recently on needed repairs. When the radiator gave out with a slow leak. I tried putting this stuff in plus Jb weld on the crack.

Worked for a week or so then starting leaking again. Ended up getting new radiator, hoses and thermostat. When draining the stuff is little metal flakes probably all over the engine and water pump ect.

Not good will need to flush out again. Bar makes great products. But this does not work for every car.

Have a 2004 Kia Rio I’ve been doing a lot of work on. Just when I think I’m done, something else pops up. (I’m sure you know the feeling. ) Radiator started leaking. Before I freaked out and bought a new one, I did my research and discovered this.

Over the last 2 years I’ve added about a bottle-and-a-half. I get a small leak, pour in what I can till radiator’s topped off and that’s it. Six months later another small leak. Lather, rinse, repeat – lol.

Imagine if I waited a bit or drained enough out to add a full bottle, might really seal it up but this way seems to do fine. All I know is I haven’t had to replace my radiator yet! Yay! :D.

I couldn’t find where i was loosing antifreeze. No drip or spots under my truck. Must be internal. I bought the bars leak l have used before and it worked. I just had the thermostat and the housing changed a few months beforehand.

Now its working great.

It stops the leak, but it also clogs the overflow hole and hose at the cap. I noticed the upper radiator hose was collapsed after driving and letting it cool a bit. Upon removing the cap, air went back in the system and upper hose expanded to normal – which is when I noticed the material from the product clogging the overflow hole and tip of the overflow hose.

I removed the clog once, but after driving just 2-3 miles, it clogged the overflow hole again. Ended up ordering a new radiator, since this is a temporary fix anyway. Just be aware that this might happen and overheat the engine, especially if you have too much fluid or it’s overflowing at all.

FYI, my fluid is at the max line and this is a Chrysler under 10 years old, and the overflow hole is about a quarter inch in diameter.

I have a coolant leak in my 2002 VW New Beetle. I know it needs to go to the shop, but I was 120 miles away from home when the problem developed. In what I considered to be an emergency situation, I added half a bottle, as per the instructions.

In fact, I would say that the coolant leak decreased by 80% or more! Got me in, and was considerably less that the cost of a tow. Going to the shop for sure, ASAP.

This stuff works as well as it needs to. I was able to see this work in real time. My plastic radiator drain plug broke off when trying to perform a coolant flush. I had to drill a hole in the plug before using an extraction tool to remove it.

A stream shortly turned into drops. I had to redrill the hole several times because this stuff clogged the hole so well.

Had a slight leak (as in leaking half the expansion tank a week) on the water pump gasket AND the radiator on my VW Golf GTI and a bit sceptical if this stuff would work. Put it in as per instructions and had to give it a few days to circulate from the expansion tank into the system.

Glad to say since putting it in I have not lost a drop of coolant. I would recommend it for small leaks and as a preventative additive.

With a seeping head gasket on our 1991 Vanagon, and not yet able to afford the expensive repairs, the Liqui Moly Radiator Stop Leak has held the leak at bay and given us many more kilometres on a tired engine.

A flush is not required which makes it more convenient, especially on a Vanagon that takes 18 litres of coolant. I would definitely recommend this product and will continue using it as needed.

Without a doubt this is the best stop leak I’ve ever used. I have tried plenty on various cars and came upon this one years ago. So far I have used it to permanently repair several heater cores on our own as well as several friends and family member over the years.

Also have fixed 1 radiator and 2 gm intake manifold leaks (very common). A couple years later and still going strong. Just some things to know. This stuff performs miracles but it can only do so much.

If you have put in 1 bottle of this stuff and it did not solve your problem then you probably already over heated your engine and caused a crack in the head too big for any sealant to fix. Also it can’t fix plastic radiator end cap leaks or hose leaks.

Yep, there are people I’ve known dumb enough to think it can. And don’t put in more than 1 bottle or you will make problems worse by sealing up every water passage in your car. More is not better here.

My van was not overheating, just leaking so I used this in my coolant system when I could not find where the leak was coming from. On the bottle it says you do not need to drain the coolant, but it did not specify that you need to have fresh coolant.

After using this product my car overheated in less than 15 minutes. When cool I checked the levels in the radiator and found that there were fiber-looking clumps all throughout. After checking the website “You must apply our stop leak products to a clean fluid system.

” My radiator was rusty and had calcium deposits before using this, but if the bottle had indicated this disclaimer I would have done a formal flush before using it. I then proceeded to use various radiator cleaners to try to get the fiber clumps out to hopefully get the overheating to stop.

The glitter is still there and holding strong after 5 flushes with no indication of stopping. I think this product would have been great if it hadn’t bonded with the rust in my radiator, but I had to replace it because it sealed up the fins.

Rating it low because the directions on the bottle are incomplete.

Coolant was spewing. Thought it was the water pump. Replaced that and then found the leak at the intake. Chevy s10 with 250K miles and I didn’t think it was healthy enough for major surgery, so tried this.

Still leaking after the first start, but then let it sit like the directions said, and then nothing. Not a drop. Been about 2 months and It’s still holding. I really didn’t think it would work, but it sure did.

Used a full bottle. Before, you use this, you will want to make sure that you don’t have coolant going into your enigine. Check you oil for any signes of water. This stuff works great in your water passages, but if it makes its way into you engines innards, I think really bad things can happen.

My radiator developed a large leak, a new radiator is about $200. 00. I have tried stuff like this in the past and they are usually temporary fixes. My Ford Taurus doesn’t allow direct access to the radiator it has a large plastic reservoir.

I called Bar’s Leak advice line and they recommended PLT11. They said to mix the can of stop leak in a container with hot water first to dissolve the pellets and remove the top radiator hose and pour it in there.

It stopped the leak immediately. So far so good, only time will tell.

Tremendous and safe for your cooling system. Stopped my streaming leak the size of a pencil lead when other brands couldn’t. The pellets are the difference and what makes it “heavy duty” capable of plugging the larger leaks.

Important to idle the engine at least 30 minutes and until the leak visibly stopped. Been permanent since I then added 4 Oz of K-Seal product with (copper small enough) highly precision and smallest particulate to make it suspended then available for any future seeping that could develop, miracle that its really “cementing” where it’s needed to prevent any later seeping.

My Toyota with temperature controlling hvac works fine and wasn’t diminished for heating and a/c, engine cooling system working normally. I expect to be able to get continued service on the radiator and when it’s diminished I’ll replace it.

Tremendous!.

I went into this thinking it wouldn’t work at all and possibly cause other problems. Minor head gasket leak that was getting into the combustion chamber and blowing out the exhaust, but not getting into the oil.

I would watch a small bubble rise into the overflow tank once every couple seconds, and over the course of 100 miles or so would be putting in a half gallon of coolant. Since it was fighting against the compression I doubted it would be able to work its way into the hole and plug it up.

I followed the “less is more” method that others on here had good results with. I drove the car to work to get the coolant up to temperature so the thermostat would be open and ready to cycle coolant.

Got to work early and poured roughly 4 or 5 ounces of what looks like robot vomit into the overflow tank, turned the heater on full blast, and let it idle for about 30 minutes with the cap off the overflow tank.

I watched the typical bubbles come up into the tank every time the cooling fan would kick on, but noticed they stopped appearing on the last couple cycles. 9 hours later drove the car home as usual and checked again when I got home, no bubbles and coolant had remained at the level I left it at.

I’ve been driving it for a couple weeks now and have even gotten on it fairly hard and haven’t lost a drop of coolant yet. I’m actually in shock. We’ll see how long it holds up, and if it blows I still have 11 or 12 more ounces to try hitting it with again.

If I get a few months out of it I’ll be happy. Please note that if you have a head gasket leak on a car you really want to keep, do not use this. Bite the bullet and get it repaired properly. On the other hand, if you have a 32 year old car that you didn’t spend much on and are just using as a beater, it’s definitely worth a shot.

I took my 2010 Land Rover to a mechanic because it was leaking coolant. The exhaust was sweet-smelling and there was no coolant dripping from anywhere in the engine bay. I suspected a leaky or blown head gasket.

I let the car sit for 3 or 4 days and upon start up there was a big puff of white smoke and I got the check engine light. Cylinders 4 and 6 had misfired upon start up. I took it to a mechanic to get it checked out and he confirmed a head gasket leak with an estimated cost of repair approaching $10k.

I decided to look for a cheaper alternative to at least postpone having to spend so much money on a repair on a car I had just purchased (used with 110,000 miles) and I found K-Seal. I read another reviewer who suggested not putting in the recommended amount, but just a few ounces, which is what I did.

I put in between 2 and 3 ounces into the coolant reservoir and followed the instructions. The car has a 5 liter V8, which is small compared to the engines K-Seal is designed for, so that made sense to me.

I took the car to another mechanic to get a second opinion about the head gasket after putting in K-Seal. I told him I had put a gasket sealer into the car and he poked fun at me for doing so, saying that those things never work.

However, after checking the vehicle, he could not find a leak anywhere. He told me the head gasket hadn’t blown at all. The vehicle drove fine! The exhaust didn’t puff white smoke anymore nor did it smell sweet.

It has only been a couple of weeks, but it appears the leak has been sealed. I am very impressed.

OK here’s the deal. I have a 1999 Ford F250 with a clogged radiator/heater core and when towing it was always over heat when towing a heavy load (5000lbs – boat and 1800lb in bed) during summertime heat of 100F degrees.

1st cleaned radiator out with Irontite ThoroFlush which made my heater core leak like a babbling brook. Approx a pint of water would drip on passenger side floor in 5 min or LESS. So I read and decided to give K-Seal a try as replacing the heater core is a little tough but doable ( 4hr job for a DIY if you don’t break any other parts along the way).

Literally after about 5 min of pouring in K-Seal in radiator the massive dripping under the heater core started to slow down to a drip. then NOTHING. ZERO water. THIS STUFF IS AMAZING. Directions say to leave it in, no need to drain everything and refill with antifreeze so I have kept it in for now.

I’ll replace with regular antifreeze soon but if you have a leaky radiator/heater core, this is worth a try to delay costly repairs (if you don’t work on cars) like I can Hope this helps anyone deciding to give this a try, currently under $20.

For the record, these are more for leak prevention then they are for stopping leaks. These type of tablets are added to all new cars at the factory to ensure a water tight seal in the cooling system.

If you have a small, or extremely slow leak, they may be able to stop it. However, you should always add these to a cooling system in which you do a full coolant flush or hose and/or radiator replacement.

They will work in all engine types with all coolant types.

I had a tiny leak somewhere in the lower part of the cooling system that did not show up using the pressure test method of detection at the shop. My mechanic suggested trying a sealer. I purchased the 2X concentrate originally then I called the Bars Leaks tech support line for help with application.

They suggested using 3 of the tablets instead. Got some of them and used as directed. Worked to repair my leak. I recommend them now, at least, for my kind of leak.

Edit — After about 1 year, Bar’s Leaks stopped working. The gaskets on my Oil Pump and Valve cover had completely worn out. Cost a couple hundred dollars to replace, but the oil leak is gone. That said, getting 1 year of driving out of a bottle of this stuff still leaves me very impressed.

I’d use Bar’s Leaks more as a way to get you to a spot where you can get your car fixed instead of an end-all solution personally. 5 stars for 1 year of stopping an oil leak at the cost of $7. Original Review I can’t believe this worked.

I had one of those “everything went wrong” moments with my 2001 Camry. For a few days in a row I noticed a burning smell when I got out out of my car. Third day I noticed it, checked the oil level – nearly empty.

I had changed the oil a couple of weeks prior so this was a bad, bad leak. Drove to a mechanic who only gave bad news. They said they saw multiple leaks on it, and that it’d be somewhere between $1500-2000 to fix.

Took it to a second mechanic who said the same thing. On the way to the second mechanic, the check engine light flipped on, the burning smell was worse than ever, a brake light burnt out, and I was about ready to bite the bullet for the repairs.

On a whim I bought a bottle of this stuff. For 8 bucks what the heck, why not. My engine had lost enough oil in a couple of days to add the full bottle of the engine repair. It said to drive it for 100 miles for best results so I visited a friend that evening 200 miles away (probably not my smartest moment since I was having all the car troubles but whatever).

I pulled in and looked under the car – no dripping. Spent the night and the next morning checked under the car. There was a puddle maybe the size of 4 or 5 drops of oil. Since driving home from the friends (1 month ago), the oil hasn’t leaked a bit.

Took it to another mechanic who said everything seemed to be looking great. I’ll check the oil once a week for awhile then probably longer intervals, but it seems like this stuff worked. Even if I have to add a bottle of it every so often, it’s way cheaper than the quotes I received were.

I was (and still am) completely dumbfounded.

Purchased this after going through You Tube University looking for a slow radiator coolant slowly disappearing Fix. Found this particular Bars product that allows to be used without flushing radiator.

Shake well install on a cold engine, let run for 15 to 20 minutes idling. In my opinion it wasn’t until I drove it the next time for almost an hour did it work fully. The metal particles find the small leaks and plug the holes.

I did find one leak at the plastic side part seem of the radiator that was weeping at the bottom near but not at the drain plug but seem. Radiator $175 plus labor or $12 becomes a no brainer. This stuff worked.

About a year ago I had a pretty decent leak in my radiator and had to fill my jeep with coolant anytime I hit the highway. Well I decided to use this product and it worked surprisingly. HOWEVER, if you do not flush it out within 8 months it will grow into a sludge that completely clogs up the system and will not let the coolant move properly through it.

DO NOT USE THIS PRODUCT UNLESS YOU PLAN TO FLUSH THE SYSTEM!.

My older Satarn was running hot, obviously leaking water from Raditor. The heater would quit working and it was deathly cold. I was working part time and did not have any money for costly repairs, especially given the fact it was an older car.

I was scared that I would break down somewhere though, and me being a female was really worried about that, and also worried that by running my card with it running hot it may blow the engine. I found this product online and it was pretty cost effective, so I gave it a try.

Directions were very easy to follow, even for me, whom doesn’t know much about cars. It worked like a charm, never had any more problems with leaking and my car did’t run hot again. It saved me tons of money I didn’t have for a costly repair from a mechanic.

It was a God Send and I would highly recommend this product.

Took my car to get brake pads done. Whilst parked up and engine running i noticed red coolant running into gutter as it slopes somewhat. I looked under car and coolant was dripping and it looked like everywhere.

Must be radiator or hose, even the t bar water pump under radiator which my car has these are prone to leaks also. Anyways i panicked like you do and thought ive got to go to Halfords. Car made it there although was getting hot.

I bought 2 bottles of Stop Leak. Waited a while to get coolant tank top off as it was overflowing. Got top off let pressure out slowly without getting burned and poured in 2 bottles! Let coolant drop slightly then topped it up with anti freeze, put top back on.

Left engine running with heater on full and took it for a spin. Voila! seems to have done the trick for now. Coolant temps are normal and i have warm air from vents. This stuff is great, dont know how long it will last but it works for now.

Just ensure you have coolant with you just in case.

Unfortunately I won’t be buying this again! I have a temperamental leak on my Jag a couple of times a yr and I usually buy a gold Holts which does the job. However there was no holts in stock so had to buy this.

It didn’t work after a few days so returned to store and still no holts so had to buy another bottle but still no joy! Ordered gold Holts online and fixed problem immediately!.

I had developed a small radiator leak. I don’t have the money to keep going to garages and Google told me to get a product like this one. I checked Halfords website and this came up as very good. It was also a good price.

Took it home, followed the instructions and it worked – no more leak! Quick and easy to use for us ‘car dummies’.

Follow the instructions. Stopped a small leak on the radiator immediately. Still working 6 months later.

I have an older Subaru, now has 280k miles on it all my own. About 5 years ago I used this product on a recommendation of a friend as the car was getting older and had a very small leak. It worked well and held up a long time.

Recently after taking the car to a shop to fix what they said was a leaky hose and getting a huge bill, I still had a problem and nearly overheated twice. So tried K-Seal again. The slight smell of coolant is gone, the car appears to have a bit more power and the coolant has not gone down at all since using.

I highly recommend for older cars where you are trying not to dump too much money into them. I know some people say there are risks it might bind up the radiator or other things but older cars , not much to risk.

Everyone I know including my mechanic friend has had a good experience with this product.

A number of years ago I noticed some coolant leaking from my ’91 Nissan D21 2. 4 liter pick up truck near the front of the vehicle approx. on the side of the radiator near the overflow tank. I had determine I was experiencing a head gasket leak along the intake side of the cylinder head.

This vehicle basically had 300k on it and I really did not want to, nor did I actually had the time to pull the head off. I had read about K seal and decided to give it a try. Well, that was about three or more years ago and the engine is still running just fine with no signs of leaking what so ever.

This product is “Out Of This World”!!! Thanks So Much For This Wonderful Product!! A Life Saver!!!.

This product comes in the cutest little container. I just had to mention that. Anyway, I was smelling a little coolant from car overtime and was noticing a slow decrease in the reservoir, which I first thought was condensation, from cold temps.

Although, I hadn’t really noticed that before. you know how sometimes you want to make yourself think something is one thing to avoid acknowledging and maybe another. lol. I turned out to be an extremely slow coolant leak.

I poured about 8 oz of the 11 oz of this product in the reservoir and a couple of days, the slight cool sent was no longer there and that drip under ceased.

I tried with my Mitsubishi Galant Car. I followed the given guidelines as per the pack. But did not work it for me.

does what it says on the tin, brilliant

Perfect

This actually worked in my application! My radiator was slowly leaking coolant in the middle left section. I had to refill the reservoir once a month and it was smelling hot coolant every time I got off my car.

I was doubting if this would work, but gave it a try. So far so good the coolant leaking I believe it stopped. I have had not refill my coolant reservoir anymore and no more hot coolant smell. I suggest you try this before taking the car in for repairs.

This is to the one that commented not recommended 2 years ago. I bought it a year ago and it worked. I don’t even know where it’s leaking at. But it just started leaking again so I’m going to buy some more it lasted a year so I think that’s a very good deal considering a radiator would cost me over $100.

My 21 year old vehicle sprung a small leak in the radiator. Following the instructions, I tried this powder. No more leak. Easy and very low cost repair. Since my system only holds 8 liters, I only put in 1/2 of the powder, keeping the rest for later.

Highly recommended.

I had a major leak of coolant happening in my little old suv. Every day I’d have to check and refill coolant. Eventually I decided that I may aswell try this stuff but really expected nothing. With the major leak my system had basically been flushed multiple times already so I just dumped the whole bottle of sealant straight into radiator (not the clear overfill container but metal cap to rad) and then added the coolant.

Ran my SUV for 10 minutes with the heat on high (heard that can help?), topped off with a touch more coolant, ran it again for 10 minutes and haven’t had an issue since then. It’s only been 1 week since used so will update if things change but was worth the $$ for me.

I put the whole bottle of this product into my 1999 Ford F150 XL on a cold engine & started her up. As usual the leak started again very heavy & I doubted very much whether this stuff would work as the leak was just pouring out of her quite badly.

It was still going a half hour later & I thought there was no way this was going to work. Then about 5 minutes after that it started to show some signs of slowing down a little. Five minutes more & it slowed to an occasional drip & then stopped dripping completely.

I then drove the truck a few blocks & checked it again, letting it idle another 20 minutes & continued monitoring it. Well it seems to have worked & I have no more leaks. Seams to be holding so only time will tell.

My 2005 Jeep Grand Cherokee, 5. 7 Hemi engine, developed a radiator leak, which required adding a quart of cooling fluid every 4 days. It is a major job to replace the radiator. I added the K&W stop leak to the existing coolant and the leak stopped, within 1/2 hour’s driving time.

I waited 2 days and then flushed the entire cooling system and installed new coolant. The flush was NOT REQUIRED, but my antifreeze level was very low. Still NO leak after flushing system. I have tried many other such products over the years, but this product is the BEST!.

The product fix a coolant leak at my water pump. But if you put incorrect amount of the product your car can overheat in some point after the use. I correct my mistake just flushing the coolant system and the car temp get back to normal and with no leaks !.

Bought this product about a few weeks ago, after i just replace the lifters. Notice a small slow dripping from the headers gasket. Retorque the bolts and coolant was still dripping. Decide to buy the K&W product and give it a try, and it work so far.

Just FYI,(my experience) i needed to flush the heater core, engine was getting hot and the heater core was clogged up with the product substance. Flushed the heater core, and unclogged it (It might need another flush).

I give it a thumbs up.

I have used this and Holt’s Radweld Plus with great success for many years. I have found this is superior to products that cost 3 times as much and is very easy to use. Just make sure you add it (with care due to hot liquids) when the engine is warmed up and circulating , so it goes straight into the system and isn’t left in a non moving coolant bottle for ages.

This product is so good it can even seal small leaks in the head gasket which is a very difficult and expensive or repair to undertake if one chooses to replace the head gasket. Try this cure first.

Had been loosing 1ltr of coolant a week through hose joints. Was sceptical of any of these quick fixes. Added the seal it & for the last six weeks I havent needed to top up! Great fix for minor leaks.

Very much recommend it. First review Ive done but was impressed & felt compelled to share.

followed instructions to the letter, flushed system and filled with new coolant, had a small leak at the thermostat housing, the product worked for a couple of days, but now leaking again. Might work for others, but didn’t work for me.

My brother bought my a bottle of K-Seal yesterday. Both he and I have the same sketchy 3. 6 liter Pentastar V6. It worked for his Jeep Wrangler K-Seal stopped the leak from the Blown head gasket in it’s tracks.

On My Dodge Durango my Head Gasket damage is too extensive, K-seal did not work on my Engine, didn’t do squat. We both have the same engine, but my Head gasket is in significantly worse shape. I am going to drain the cooling system today and try a different Product.

The fact that it worked on my brother’s engine is proof that if you know it’s a blown head gasket early enough, this product will work great. Otherwise you’ll just be wasting your money.