Another HVAC Vacuum Thread - JeepForum.com
 
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post #1 of 13 Old 07-08-2019, 03:14 PM Thread Starter
crayzkirk
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Another HVAC Vacuum Thread

I've been reading about the HVAC Vacuum threads and the one thing I haven't seen is how to replace/repair the black vacuum line that comes through the firewall. I pulled the battery tray and verified that the hose and vacuum storage are intact. I have replaced the vacuum valve as well. The cruise works however it's a bit sluggish. A/C switches to defroster vent when climbing hills. I also have the wet passenger floor issue however the drain is clear. Also replaced the inlet screen with the service part and performed the procedure to clean the drain as per the TSB.

Is there a way to get to the vacuum line without pulling the dashboard? Through the radio opening? The glove box? Or am I just going to have to bite the bullet, have the A/C evacuated and pull the dash to fix a vacuum hose?

1998 ZJ 5.2 Special Edition...

By the way, what makes it a special edition?

Thanks,

CrayzKirk

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post #2 of 13 Old 07-08-2019, 05:00 PM
wingless
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It might be possible to "only" remove the dash pad, then carefully cut a blindly-placed hole through the dash frame, as shown in my similar, but different '94 ZJ.
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post #3 of 13 Old 07-09-2019, 10:38 AM Thread Starter
crayzkirk
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Yikes!
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post #4 of 13 Old 07-09-2019, 11:51 AM
wingless
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That is the easy part to remove...


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post #5 of 13 Old 07-09-2019, 05:21 PM Thread Starter
crayzkirk
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Thanks for the picture. I found an online factory service manual where it shows removing the dash without taking it all apart. It shows 2.1 hours to replace the heater or a/c core. I know that at some point, if I want to keep the Jeep, I will have to do this. 250K miles and the rocker panels are pretty rusted living in the Midwest. I think I will look around for the rear window washer hose where it goes thru the firewall and see if I can re-purpose that.
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post #6 of 13 Old 07-09-2019, 08:00 PM
KiloWatts
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If I ever have to replace the heater core I'll probably do a whole lot of rewiring while I'm at it.

1996 4.0 L6 RWD
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post #7 of 13 Old 07-11-2019, 08:47 AM
jeepjeepster
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Why do you think the vacuum line is bad behind the dash?

The seal could be bad for the drain tube thus causing the wet floor. The seal in my 94 fell apart when I removed the HVAC box.
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post #8 of 13 Old 07-11-2019, 02:01 PM
mikem350
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A/C switches to defroster vent when climbing hills. I also have the wet passenger floor issue however the drain is clear. Also replaced the inlet screen with the service part and performed the procedure to clean the drain as per the TSB.

Get one of those cheap brake bleeders from HF and go over those hoses and components feeding the cruise and the vents (thru the firewall). A leak will cause vents to switch.

My experience for wet floor is to seal the drain at the firewall where it pokes thru. Its kinda hard to get RTV or caulk in there, but give it a shot, check the archives!!!! Seal from pass compartment under glove box, peel back carpet, etc. Try to dry it out first!

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post #9 of 13 Old 07-11-2019, 03:13 PM
JonS
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I cut my plastic line on the engine side and slipped rubber vacuum hose over it to connect that end to the “T” connector and it is a permanent fix.


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post #10 of 13 Old 07-12-2019, 09:17 AM Thread Starter
crayzkirk
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The seal on the HVAC box is good, the vehicle was in an accident so I'm not confident that the leak isn't from somewhere else. The seal is not wet when I look at it. It almost looks like the water is running down in from the side panel. I really need to pull the seat (problematic because the bolts are rusty from the water) and carpet to see where the water is coming from.

I have a vacuum gauge that I hooked up to the T at the place where the HVAC feed is hooked up to. It holds vacuum there. I pulled the battery box and checked the vacuum box and all hoses. The plastic line isn't broken or cracked and has no apparent breaks before it goes into the firewall. The big electrical cable makes it difficult to see. I will use the gauge inside the car to verify that it's losing vacuum on the supply. From the pictures, the supply goes down, around, then up and over the HVAC box so if the break is inside the firewall, my options are limited.

I have a MightyVac so I can check the hoses and vacuum motors, I replaced the HVAC controls thinking that it might be leaking however it's pretty simple inside and doesn't look like it's prone to failure (steel ball covers the appropriate port).

Thanks for the suggestions...
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post #11 of 13 Old 07-12-2019, 09:52 AM
1996maroonzjf
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Garage
You might want to take a look at this -
http://dodgeram.info/tsb/1996/24-01-96a.htm

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #12 of 13 Old 07-12-2019, 01:19 PM Thread Starter
crayzkirk
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Quote:
Originally Posted by 1996maroonzjf View Post
You might want to take a look at this -
http://dodgeram.info/tsb/1996/24-01-96a.htm
Thanks... I will see if that helps. I remember reading that a while back. I changed the check valve on the main line and it seemed to help a little or I just imagined that it did.
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post #13 of 13 Old 07-14-2019, 08:04 PM
Boone96ZJ
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I had a check valve in the exact position stated in the ram tsb and it would still go to defrost when on full blast ac. I moved the check valve where it is right next to the manifold source. Non problems since. Think about it, if check valve is at HVAC line, you only have "stored" vacuum in that tiny little line and once you exhaust that stored vacuum going up hill, poof back to defrost. With check valve at manifold, youre actually using the vacuum resevoir as intended.

96 5.2 242 3" 32x11.5
https://www.jeepforum.com/forum/f13/1996-grand-cherokee-laredo-5-2-a-2570290/
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