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Vacuum Basics?

7K views 7 replies 5 participants last post by  Molonlabemike 
#1 ·
Hello,

I have a '97 Wrangler. I have 4 wheel drive, but no cruise control, or really any other extra featurs. It is an automatic transmission 6 cylender. My heat / air conditioning will not rerout through the vents, and is stuck in the defrost position. After reading several posts, it sounds like I need to look under the hood for a vacuum leak. I have a few questions about the vacuum system.

1. Where should I look for the leak?
2. Which systems run off of the vacuum system?
3. What are some tell tale signs of a vacuum system problem?
4. How does the vacuum system work?

I'm fairly mechanically inclined, but I'm definitely no expert. I would really appreciate it if somebody could answer these questions for me as though they were teaching somebody who needed to be spoon fed. Also, any photographs would be very much appreciated.

Thank you! You guys are great!
 
#2 ·
The vacuum system on the Jeep is really simple and only controls vent position and cruise control. There is a vacuum hose that comes off the intake manifold, near the back. From their it travels along the firewall to the passenger side where you will find a T fitting. One way goes to the vacuum reservoir inside the fender and the other goes into the cab. From the cab it travels through the dash to the HVAC controls, then splits into all the separate hoses to control the different vacuum canisters that control vents.

I don't have cruise control, so I assume somewhere under the hood there is another T fitting or something to go to the cruise control.

Basically look for anything disconnected or any cracked hose.

BTW 4wd is not vacuum controlled, it's mechanical in the t-case.
 
#3 ·
Start with this picture,



Number 5 and 2 on the lower right is where the connection on the intake is, the elbow of number 2 falls off the port ( 5 ) , reconnect there and put a ziptie around it. If its connected, follow the diagram until you find a broken or cracked hose.
 
#5 ·
I figured it out guys. Thanks a lot! I had to stand stand up on the front bumper and lean way over to feel for the nipple that that hose hooked up to. I got it on and it works! I think it's the first time in years that thing has pushed air out of the vents. Thanks again!
 
#7 ·
Glad you got it, FYI it is easier to see that connection ( 8 ) if you lay under the right side of the vehicle and look up along the front of the firewall you can see if the box has come loose or if the hose you attached has any cracks that may cause it to come loose again.
 
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