i think you had something in your radiator that you didnt flush.

or you had a dye somewhere and it finally spread out.

It doesnt look like corrosion. Turn your system off and press your tubing, does it feel pressurized?

For now i would just flush your system if your temps arent affected.


Your FUSION IS ALU! just to let you know.


i know what it is.

Im guessing you had more dye on the inside of that GTX top then nomal, and its bleeded out into your system.

your mixing metals there bro. the GTX isnt safe and has been shown not to be safe unless you get the copper top.

The fusion nb block is also alu. You have a classic case of a mix loop system. You need water wetter.