Just got done replacing the heater core, and now that it's all running again i hear a hissing noise whenever i step on the gas and and idle. it increases with rpm, stops at about 2000,then starts back up again at 3000. i'm pretty sure it's not a vacuum leak, it runs fine, and I made sure all the vacuum lines were connected on the HVAC. in park if i step on the gas i can hear it suck almost like the sound the throttle body makes. Does anyone have any suggestions as to what it could be?

 

My guess would be a vacuum leak. Maybe one of the lines got a crack in it or something when you moved them.

 

most likely, thanks for the input

 

Just unplugged the vacuum line to the HVAC, noise is still there so it has to be coming from somewhere in the engine bay, anyone have any suggestions where to look for one? It almost sounds like the throttle body is causing the noise, but I don't see why all of a sudden it would start a leak also when the throttle is wide open the noise goes away completely

 

Maybe you have a bad vacuum hose in the engine bay then.

 

well on the way home from the GTA 5 midnight release last night my vent controls stopped working completely. It almost sounds like the leak is coming from the A/C blower motor switch (the thing with the heat and fan settings on the dash) could it be possible this somehow went bad and can't keep vacuum? it makes no sense why cruising down the highway it just switched to defrost and i can't change it
Edit: just drove to the hanger and I can tell it's definitely leaking from the a/c blower controls

 

Yep that's definitely a vacuum leak somewhere in the system there. With no vacuum present it defaults to defrost.

BTW, you liking gta 5? I was too busy last night to go to the midnight release, so I'm probably going to have to get it either today or tomorrow.

 

Man it's great! I was playing it until 4 this morning. 8a.m. classes were brutal today

 

Yeah, I'm glad I don't have any 8 am classes. I was in the robotics lab until 9 last night, then had to do a couple assignments, so I was too tired to go get it last night, plus if I got it last night I wouldn't get any work done today, which I need to. Really I'd like to wait until the weekend to get it because I have to study for an exam this week (which I probably won't do if I have the game), but I heard that they only give you 2 days to pick up a preorder from gamestop.

 

Soapy water in a spray gun or toy squirt gun. Spray and look for bubbles!