Want to make a 16 feet long molex cable for my pumps

[KING2882000]

Hello

I dont want to have my Radiators and Pumps near me so i wanted to make two 16 feet long molex cables for my two aquastream xt ultra pumps. Is there a Risk of cable fire, if i cut a molex extension in half and solder 16 feet of 1.5mm² cables inbetween them? I use a Dark Power Pro 11 1000W PSU.

Thank You

 

[KING2882000]

I already asked that in a German Forum and they told me that in worst case could run the full 40A of my PSU Rail through that cable and it could burn if there is some kind of error. But if that is true, why are my normal 60cm Molex cables not already burning? I just dont want that my cables burn. Btw I would cover every single soldering point with a heat shrink.