I was wondering, I just started noticing that my engine is making short hissing noises. I was wondering if this is the AC compressor noises people are talking about. The thing is, it still happens even when my AC is not on. It is concerning me. The car drives fine even with the noice, but I didn't notice it until last night. Anyone else get this noise on a GT? I have a manual. And when the car is warming up it makes this noise. It seems to happen every 30 seconds or so. The sound seems to come from the passenger side of the engine.

 

I found out the engine pops and hisses every 10-15 seconds when I put it in the window defogging mode. It's wierd.

 

Mine does it too but I imagine it's just normal noises. I'm pretty sure that when you turn on the defogger, it automatically goes into AC mode. That's how a lot of cars are at least.

Whatever it is, I'm not worried about it.

 

that's normal