K-Seal Coolant Leak, 236ml | Multi-use Car Radiator & Head Gasket Repair Sealant

Well well well, this small bottle of liquid worked perfectly, and months later still no leaks. So happy

Great product. I had a difficult to locate leak on my cooling system, the tank was empty/below the minimum line every morning. I topped up with new coolant to minimum, added all the KSEAL, then finished topping up with coolant to just above the max line & took the car for a good half an hour drive with the heating cranked up to max for the duration of the drive. Check my levels this morning & I haven't lost any coolant overnight. Perfect product for fixing the job.

My water pump was leaking, it cost me £800!! to have a new one fitted, only to learn that this is an ongoing problem with AudQ5, low and behold, about 2 years later, this new water pump started leaking also!! I did not want pay out another £800 or more, so I looked for another remedy, and came across this K-seal, I was in two minds some reviews were positive, some were not, the one that caught my eye said, you need to follow the instructions and shake the bottle vigorously, which i did and poured into coolant tank, then let the engine reach normal operating temperature, then i drove my Audi around for a good 20 minutes, I mixed the K- seal in mid April 2026 and its now mid May, there is NO leakage, so hopefully its all working, i will keep an on it, and give another update if any leaks return, otherwise I will update at the end of the year!!

Good price arrived ontime well packed, works well have used this before to cure a small radiator leak

Great product, works really well!

I purchased a bargain car that I knew would require some work to put it right. When I purchased the car the engine was lacking power and the idle speed was hunting (going up and down). As the engine oil was ok I thought I'd try cleaning out the fuel & exhaust system first using Injector cleaner, turbo cleaner fuel additives and diesel particulate filter cleaner additive to burn off any soot built up in the exhaust. After I'd tried all of those each one on a full tank of fuel I'd probably done 1,500 miles and the car had more power and the idling had improved. I then noticed the car had started to lose approximately a pint of coolant over 10 miles and I think there was a slight whitish haze in the exhaust smoke which shouldn't be there as the car is a diesel. I wondered whether I'd caused the coolant leak by using the fuel additives as they contain detergents. I suspected the coolant may be escaping via the head gasket or maybe via the exhaust gas recirculation cooler into the exhaust so decided to try K-Seal. At first I thought the K-Seal had fixed the leak but after a couple of days the car started smoking again and the coolant loss was about the same as before I had tried the K-Seal. Unfortunately during those couple of days the K-Seal had made a proper mess inside the coolant header tank and as the header tank is made of white plastic lots of copper particles and gunge can now be clearly seen coating the inside of it above the coolant fill level. I have since wondered whether the previous owners may have already used a leak repair to hide a head gasket problem and if so whether it would have impaired the efficiency of this product but have no way to know if that was the case. I decided to try one more cheap fix before considering a garage repair so purchased a competitors product that was cheaper than K-Seal and does not contain all the copper particles. The cheaper product has currently stopped the coolant loss but it would have mixed in with any remaining K-Seal in the engine block so maybe they are complementing each other now. In conclusion, this probably does work in many cases but in my case, it didn't work. I am pretty sure that in many other cases it probably also makes a proper cosmetic copper splattered gunge mess inside the header tank. In hindsight, I think I'd only try the K-Seal again if I could add it directly into one of the cooling pipes so the whole bottle doesn't start off in the header tank or alternatively I'd add it to a warm system so the thermostat would already be open. Also if there is ever a next time on another vehicle personally I'll try the competitor's product first as it was cheaper and didn't make a mess inside the header tank.

Used this several times in the past works great

Use as instructed and its the best on market

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.