Problem with unusual noise from engine compartment

[rutledj]

On my 2002 4runner, while drive down the road, I hear what sounds like a loud hiss sound that last for 2-3 seconds and goes away. It does this the whole time I'm driving. I thought after searching here that it was related to the brake system but it doesn't do it when braking.

I was able to hear it one time while parked and the hood open. It sounded like it came from around the brake MC area but couldn't be sure.

Any ideas?

Thanks,
Rut

 

[994runner21]

Check your charcoal canister. Large black box located by your MC. Your a/c will aso make a lil hiss noise for a few sec everyonce in awhile if thats the case everyrhing is fine

 

[rutledj]

Hiss may not be a good way to describe it. It is loud as you can hear it inside the cabin going 70mph. It almost sounds like something releasing pressure for a couple of seconds.

 

[rutledj]

It is associated with the ac. I just drove about 35 miles with no noise. Turn ac on and it comes back

 

[994runner21]

Yeah, I have this noise. Since i owned the vehicle matter of fact. I don't believe its anything really. I have just left it, and have not had any problems (a/c works, nothing seems to be out of order).

 

[THEREALTOR1]

Anybody know exactly what this is? My girl has a 2000 Limited and her's has produced this noise twice in the last week or so (both times right after starting it up and turing on the AC). Scary freakin noise (almost sounds like some high pressure air canister "blowing off"). It also sounded maybe like a belt squealing over a seized bearing or pulley or something. So is it the charcoal canister or something else completely different?

EDIT: Also curious if the other people who are experiencing the issue are in Limiteds also? My 01' sport does not have the fancy digital control that her Limited does (not yet anyway ), and i'm just curious if it's somehow tied to that setup (not necessarily the digital display directly itself, but maybe the system as a whole is set up slightly different to accomodate that design)? Just curious.