hvac vacuum leak 97 XJ

twinkiedooter

New member
My 97 Jeep GCL has a selector switch problem. Heat works fine and dandy. No A/C though. The heat only comes out of the defrost vents and I was told that I have a vacuum leak somewhere in the system. I need a schematic to see just where this leak could be but can't find any schematic online that makes any sense to me. I took some photos and saw this under the hood that was not connected to anything. The second photo shows an orange plires end where the part is that looks wrong. Please help as last winter I damn near froze to death as I live in Northern Ohio and it got down to zero a lot even in the daytime. Many thanks.
 

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Looks like you got to do the same job I've been procrastinating on . A few years ago I had my dash off and didn't change the hard emissions tubing . Now it's come back to bite me. The vacuum signal supply from the manifold tee has dry rotted from under hood temperatures and have way where it penetrates the firewall . To do it right , I'll have to work from the inside but the glove box is molded plastic on an XJ so the dash must come off ( again). I might try to dream up another short cut but as I remember , the vacuum signal line TO the climate control and line to heater valve sit tightly on the defroster ductwork and may be difficult to pull through . In your case , you can try to remove the center cluster to see if you can manipulate the line if it's not too hard to fish through. The idea is to connect the new line to the old one and pull,it through if there's enough room and the line cooperates. But the problem and symptom your having , loss of floor vents and face vents , only defroster vents is the same as me. Happened to me recently when the temporary repair I made quit due to crumbled plastic tubing. That tube in the photo has a valve to prevent vacuum from bleeding back so when the dash control is selected to off position . That valve should receive its signal from a manifold tee . Look for a connection on the intake that may have an open fitting. Of the hard line going inside the dash is good and only the line under the hood needs repair , you can just find what tubing will fit and run it . I believe it's either 1/8" or 5/16" . But measure to be sure. You want a tight fit but not so tight you can't get it on without fight with it. Should go on with reasonable force . If you have a hand vacuum pump like those one man brake bleeders you can hook it on the the plastic valve and draw vacuum to make sure of the vacuum motors under the dash are working when the lever on the dash control selects different functions. That will confirm if all else works. Hope this helps.
 
What RPM do you idle at?

The image isn't clear enough for me to determine if that is the tee that leads through the firewall to the HVAC.

To find vac leaks:
Start at the intake. Most connections in the intake are vacuum lines. A leak at any of these can effect vacuum level and cause the hvac issue. Visually inspect lines for cracks and connectors for dry rot. You could use a spray of water or wd40 or carb cleaner while idling and listen for a change in idle to detect a leak. Also there is vac revisor under the battery that needs to be inspected.
 
Today I happened to be out at my mechanics looking at a car and I told him about this 2" tit sticking out of the line. He looked at it and I told him about how there was supposed to be a hose at one end and hooked into the firewall. I had looked at my neighbor's 96 XJ when he came home today and traced back that tit to see where it went. My mechanic found the firewall male connection and sent me to get some tiny hose to hook up the tits to. The photo of the orange plires says it all. Where the connection into the firewall was was just to the left of the silver heater hose. I will let you know if this works when he connects the hose in the next day or so.

I hope this works as I would LOVE to have heat this winter.
 

The line was NOT compromised but had the 2" tit thingy missing it's hosey deal to connect to the firewall.
 
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