Please note that the "Red October" had a lot of bad luck - it was spotted by American an submarine BEFORE it turned the silent engine, so Jones was doing whatever he can to locate it again, because he didn't believe that submarine can simply disappear.
So if the Red October would turn on the "caterpillar" drive before it has been detected, it would remain silent. In other words the technology is working, the sonar operator was VERY lucky and the Soviet submarine is extremely valuable, because IT IS undetectable, unless you really know what and where you are looking for.