TSI Supercool RD8 Radiator Coolant Water Based U/V Leak Detection Dye (Self Measure Bottle), Purple, 8-Ounce Bottle

Was skeptical at first but used it and it makes it so much easier to find a leak and most of the time you dont even need the flashlight to spot it. Color is nice and bright to see definitely worth the money id buy again. Worked great for us even though the radiator is shot.

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.

This product worked well found my.leak has radiator replaced

Glows very bright

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 like it's supposed to.

Helped me locate a cooling system leak that I could not find otherwise. Was afraid I had a head gasket issue as I never saw dripping antifreeze anywhere. Found leak on thermostat housing that was getting flashed off on the manifold.

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.

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.

Good quality dye, not much more to say. Got it to find a leak in my cooling system and found 4! So yeah, works as advertised.

Worked very well. Makes it very easy to track where coolant is leaking to with a UV light. Lights up very bright when UV Light is shown on it