The factory uses spring clamps for the heater hoses. These automatically compensate for changes in the rubber hose, but if gear clamps were used, they may need to be tightened. But look carefully, the leak may be coming from the elbow fitting into the tensioner assembly - these are sealed with an o-ring that may need to be replaced. Also, if the wrong size rubber hose was used, that may have created a problem, too. Finally, sometimes the sealing surfaces on the steel elbows and in the aluminum tensioner assembly can become so pitted and corroded that the hose or o-rings cannot make a good seal.