so my daughters 2007 volvo s40 2.4L has this massive squealing/growling coming from engine ,i checked to see if it was the diaphram so i pulled the dipstick and took off oil filler cap and there was no excessive vaccum pressure on them and it didnt stop the noise,what did stop noise was when i turned the A/C on!!! any suggestions on what it could be?

 

Idler bearing in the the ac clutch, it only spins with the ac off.

 

ty so much