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Vaccuum leak

1K views 15 replies 8 participants last post by  Night Prowler 
#1 ·
My 97 2.5 has a vacuum leak, i'm not really sure how to find it though. When i switch directions on the hvac i can hear a hissing sound behind the selector. I can hear air being blown when i have the fan on, i just cant feel it come out of anywhere. Under the hood there seems to be the same plastic vent thats behind the dash and its almost dead center behind the engine. On that tube there was a styrofoam-type seal on it that seems to be pretty busted and dry rotted away, does anybody know how to replace that? I don't even know what to search. Also i can smell exhaust gas all the time. Thanks guys
 
#2 ·
If your hvac isn't switching properly check the vacuum line that connects from the rear of the manifold and goes across the firewall, splits off and goes into the cab by the heater core tubes and to a vacuum box under the battery (common to come off that box)

That plastic that is on the firewall is the cowl drain, not sure about a seal on it though....
 
#3 ·
If your hvac isn't switching properly check the vacuum line that connects from the rear of the manifold and goes across the firewall, splits off and goes into the cab by the heater core tubes and to a vacuum box under the battery (common to come off that box) That plastic that is on the firewall is the cowl drain, not sure about a seal on it though....
Thanks alot man
 
#4 ·
Ok so i checked all of the connections under the hood and at the vacuum box and they're all good. All my connections on the back of the hvac controller are also good? I can hear the hear blowing, i just cant feel it coming from any vents. Im lost here guys
 
#5 ·
Just a "if nowhere else" do you have a vac-line with plug from the brake booster?
I've seen the plugs in the brake booster crack/go bad and cause vacuum leaks.
 
#10 ·
Have you checked the main vacuum line that comes in behind your glove box? That needs to be connected in order for ANY of your vent/defrost/foot settings to work. I just had to repair mine due to a mouse chewing this line in half. I could hear and feel the heat/air blowing, but there wasn't much forceful air through any settings.
 
#11 ·
To track down some engine and transmission noises I picked up a mechanics stethoscope. It also came with a tube and funnel fitting designed to help track down vacuum and air leaks.... I haven't used that capability yet but it was a relatively cheap tool ($20 I think) that might help locate the source of the leak.
 
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