TSI Supercool Synthetic U/V Leak Detection Dye, 1 oz, 1 Application

This stuff worked great, one ounce was more than enough. For those who said the product didn’t fluoresce in the bottle, I believe it needs to mix with the coolant/water to really light up. Remember this is to be used with a black light/UV light to see the leak. While it was bright enough to see some areas with no artificial UV light, it is ideally used with a UV light. Super bright for me, showed the leak clearly and was in an area that I never would have thought of or found without the leak detector.

Works great. I would rather not use it because is is colorful enough even without UV that I think of it as messy, and drain and flush after finding and fixing leaks, but maybe I add too much, or maybe I should just not worry about that and rinse everything when done. It is quite water soluble and rinses clean off. My son calls it "predator blood", looks the same. Definitely helps finding obscure leaks on messy engines. Be sure to put it in the radiator. If put into an overflow tank, especially a non pressurized type, it may require a few heat cycles to transfer enough to where it matters to be useful. Obviously, won't help with a head gasket leak to the combustion chamber, unless you look with a borescope, maybe after letting it sit pressurized a while. Head gasket leak to crankcase (oil contamination), you shouldn't need this stuff for. The milkshake is perfectly fine for that.

I had a coolant leak. My mechanic said that they couldn't determine where the leak was because it was very slow. After a while, the rate of leaking increased. Rather than using a leak-seal product, I wanted a real fix, so I added this dye and drove around. My mechanic said that the dye made it very easy to see where the leak was. This saved a considerable amount of diagnostic time... and saved me a considerable money. It was really easy to use. The only issue was that my mechanic said that the dye had made a mess on the bottom side of my truck.

works fantastic with a UV light - not dim illumination under light, very bright You could realistically use half the volume they recommend. --note of caution-- it WILL fluoresce brightly in trace amounts, you will have to clean very thoroughly if you're continuously chasing leaks or using it as early detection.

Works good, found puddle under my thermostat housing and made noticing the weep hole spewing water from my pump a lot easier. Very bright and could instantly notice it after running the car for a couple of minutes.

Had a leak I had issues detecting tried UV dye, pressure testing and this stuff worked. Man it stands out and it’s beyond obvious. I put it in all my cars since any leak you will know.

The bottle leaked all inside the Package. The product it self works great. But how the product was delivered leaking inside package was not to be expected.

If you have a coolant leak and can’t find it, get this!!! Makes it very easy to find. I would get a uv light, helps to see it.

Sooooo very concentrated and BRIGHT. This product helped me diagnose a gremlin in my coolant system. 5/5 stars, great product.

The only Radiator specific dye that i could find. All others are for oil and are not compatible with coolant. It works amazing and it glows really bright fluorescent yellow under 365nm uv light form a cheap torch. The ammpount was more than enough for a very large LR4 V8 with dual AC system.

Works really well, even without a black light you can clearly see the leaks, recommend.

It does the job perfectly and you can find your leaks easy

Very strong, only need a little bit to make all of the coolant extremely uv visible. Helped me find my leak