Its that small hose coming from above the intake manifold going into what looks like a sensor thats located on the firewall.



I hear a suction noise but when I press on the tube, the noise stops. What is this tube for and is it suppost to make such a loud suction noise? The tube appears to have some small cracks along the bends.

 

I think that hose goes to the heater valve. mine was cracked too, replaced it, no more hissing.

 

Lol, you think you could find an engine bay pic a little bigger than that?

As for the tube, I am GUESSING it is the vacuum line for the cruise control (based on the location you describe) and it may be hissing because there is a leak in it somewhere. Replace it and see if the noise goes away.

 

FAQ cardomain, it won't let me see full size pics.

 

Ah, just replace it, I'm sure that will take care of it.

 

This kind of looks like the hose that connects to metal pipe that connects to the PCV valve. It shouldn't hiss, replace it with vacuum hose.