So last night, two days after examining one spark plug and putting it back in, I noticed a hissing sound from the front of the car. This hissing goes away completely when I press the clutch pedal in. What is it? Could it be connected to me opening the spark plug and putting it back in? I read somewhere about a common clutch bearing problem but I thought that it might be connected to me removing the spark plug, since I didn't notice it before. The car is a 2012 Citroen C1 (similar to Toyota Aygo and Peugeot 107)
P.S the car has only done 50,000km.
Thanks so much,