I tried the same method with the boiling water and only suceeded in only burning my fingers. I eventually re-read the instructions and used a set of needle nose pliers inserted into the hose end to stretch the opening. I then used a shot of WD40 and the hose went on easily over the large flange on the green one way valve. The other thing I learned is that it does not matter which way the tiny little metal restrictor goes in the other end of the hose. The other solution is to head to your local auto parts dealer and buy a similar length of vaccum line if you go to extremes with even more heat than boiling water (don’t ask) and end up with a real bodge job. Good luck.