Liqui Moly Radiator Stop Leak | 250 ml | Cooler additive | SKU: 20132

I recently tried Liqui Moly Radiator Stop Leak in my older vehicle that had developed a small coolant leak, and I’m genuinely impressed with the results. I’ve used other stop leak products in the past, but this one stood out for its ease of use, fast action, and trusted brand quality. The instructions are straightforward—just shake well and pour it into the cooling system when the engine is warm (but not hot). Within minutes of running the engine, I noticed the coolant level stopped dropping, and the leak around the radiator seam appeared completely sealed. What I appreciate most is that it doesn’t clog the system or create sludge, which can be a problem with lower-quality products. My heater continued to work perfectly, and the engine temperature stayed normal. It’s compatible with all types of coolant, which adds to the convenience. Overall, Liqui Moly Radiator Stop Leak is a solid, trustworthy product that can extend the life of your radiator and save you from costly repairs in a pinch. Highly recommended as a temporary solution or preventative measure.

I like to always keep a can of this in the garage just in case. It always seals without clogging anything, as it remains liquid except for the amount it takes to seal the leak. My last repair was pretty mundane, but before that I used Liqui Moly to repair a plastic radiator that had a hairline crack on one of the end tanks. Not only did it seal the crack, it lasted two years before a different crack developed. I decided to use another bottle of Liqui Moly (I had replaced the coolant some time in between, so there was no longer any product in the system), and it worked just as before. A few months later, I was driving home when I saw steam rising and my temperature gauge steadily rising, so I pulled over. I figured that the Liqui Moly had failed at some point, but upon inspecting the radiator I found that the hose mount and most of the end tank had broken off, causing a major loss of coolant. Once the car was back home (thanks, AAA!), I further inspected the broken piece and discovered that I could see the previous cracks that the Liqui Moly had sealed within the larger broken piece - Liqui Moly was still doing its job, even though it didn't stop the giant crack from happening. And yes, I replaced the radiator at that point, along with all of the hoses and the water pump. The old pump still looked like it was in great shape and showed no sign of clogging or sealant residue, which boosted my confidence in the product. I still have that car and it still runs great, by the way. I also just recently had the timing chains done on another car, and it seems the mechanic left one of the radiator hoses loose. I tightened the clamp, which fixed the issue, but it reminded me to order another bottle of Liqui Moly to keep on hand. I know that if I ever need to use it again, it won't mess up my cooling system.

Audi A4 B7 with 130K miles. On the floor of my garage I discovered a few drips of coolant where my turbo/ECU/cold air box would be. I knew there were AC lines under the engine in that area and I thought maybe I sprung a leak in one of those lines. When I looked under the car I saw where the drip would form for the coolant, I was dripping off a weird spot, the K frame that holds up the engine, so it really was nothing near the far right side of the engine. With a flashlight I looked and found the source of the leak, it was coming out of the side of the aluminum engine block! There was a drippy triangle of coolant dried up coming from the same spot. Oh no! What I discovered was that my engine has suffered a BLOWN HEAD GASKET. I know this Audi A4 2.0T FSI engine runs hot but I didn’t expect it to blow an engine seal. I was bummed. So now I started my research. On the Audi forums and in Amazon reviews. I eventually chose Liqui Moly because it was highly recommended for aluminum engines. I ordered one bottle, followed the instructions with the install and everything was great, no drops of coolant on the garage. Problem solved! Then after about a month I got another small drop on the garage floor, obviously the Liqui Moly Radiator Stop Leak worked but the engine hole in the seal was larger than a one bottle fix. No big deal, I added a second bottle! Now two-three months later there is no coolant leak on the floor and the engine temperature is regular just as it always has been. This engine sealant had no adverse effect on a thermostat or anything else. Liqui Moly is made in Germany and seems to be tailored to the Euro Car industry. I can tell you it works. I’m very pleased. I would recommend.

Not enough of a leak to even see evidence of it, but enough that you can smell that tell-tale A/F smell. This stopped it for a few weeks, but it's back again now. Good thing is, this is fairly clear and doesn't pollute the coolant giving indication that it's in there.

UPDATE 2..... I drive a 2015 Audi S5. It has 140k on motor. It started leaking antifreeze at 133k miles to where i had to carry a bottle of it with me and usually had to put more in every 5 to 6 days. I am at day 35..... AND THE MOLLY RADIATOR STOP LEAK HAS WORKED 100 PERCENT. I DROVE IT FROM Melbourne FL TO Jacksonville FL ABOUT 250 MILES ROUND TRIP AT APPROX 90 MPH AND THE FLUID WAS AT THE SAME LEVEL AND NO OVERHEAT ISSUES. I ALSO HAVE A REVIEW ON VALVE COVER LEAKS I WAS HAVING ISSUES AS WELL.

Clean, easy to use and is effective in solving the problem. I highly recommend this product! 👍

I bought a mint 94 Plymouth Voyager with very low miles this past year, and its my garage queen. Well, seeing that it has sat a lot, and is 30 years old, I noticed the other day it had developed a heater core leak, fogging up the windows and the entire interior smelled of anti-freeze. I cringed at the thought of tearing apart a 30 year old chrysler product dashboard (brittle plastics come to mind), so I decided to take the risk with the Liqui Moly stop leak for the cooling system. Holy crap... within MINUTES of driving around after adding only half the can to my radiator, the heater core stopped leaking! And thats with HALF the can, or maybe less than that because I spilled a little of that even. Super happy it is fixed, and when it stops working hopefully I'll be dead by then and it will be the next persons problem to replace the heater core lol

Yes it fixed the leak in my radiator but 3000 miles later my water pump went out and when i opened it up, it was gunked up with this product. I did use two bottles so just be careful start with one