Hi guys, I have a Subaru Impreza year 2010. In my area, the temperature is really low, so these days I always plug in the block heater for a few hours before driving. I don't know much about cars, but I heard that if the block heater is working, it has some kind of "water boiling / running" noise when plugged in. So, every time when I plug it in, I listen carefully. And usually there is such noise. However, this morning, when I plugged it in, there wasn't any noise. After a few hours, I opened the hood and touched the engine part and other areas, they weren't heated up. Can I assume the block heater is not working? Thank you very much for your advice.