Looks like coolant

This happened to me before! My god I was so pissed. Luckily I went through multiple items to get it to work. This is going to sound crazy but it works. If you have an extra bicycle laying around take the brake adjuster of the handle bars, it’s like a little aluminum piece that has thread and an opening. I punched in the thread into the radiator and connected the hose over the brake adjuster and a clamp. Happened years ago and never had a leak or anything. It’s not stupid if it works 🤷🏽‍♂️

https://preview.redd.it/283fn9ntjk2c1.jpeg?width=901&format=pjpg&auto=webp&s=807abc52dab1fadc7f37cd5683cbcc7e2ff80c44