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Unread 03-25-2012, 02:59 AM   #1
mlhelfin
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Vacumn leak 95 Grand Cherokee ?

Last week on my way to work I just for the hell of it tried my cruise control and it worked. On my way home that night I tried it and it didn't work. Then this week I went to switch my vent control to the dash vents for my AC and it won't switch over. Its stuck on the defroster/floor vent mode. I checked some of the past archive post and it seems that the two may be vacumn related. I'd appreciate some pointers on where to start looking for my leaking lines. Thanks alot for your responses. Mark

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Unread 03-25-2012, 07:27 AM   #2
edcalli
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U can use cigar smoke to find leaks by disconnecting the lines and blowing it in the line as far as where to start I don't really know.
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Unread 03-25-2012, 09:17 AM   #3
sebian
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Or, if you are not a cigar smoker, start looking at the vac lines on the intake manifold. After 15 years, they tend to get a little brittle and start cracking and breaking. There is also a vac line that runs under the battery tray. That one is pretty notorious for leaking.
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Unread 03-28-2012, 10:58 PM   #4
mlhelfin
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Thanks for your input guys. Today while driving my zj and sitting at a stop light I could hear a new noise coming from my glove box area. Kind of sounds like speaker noise with an amped system with volume all the way down. I'm thinking that its a vacumn leak in that area. Anyone pulled the dash and glove box and traveled to that area for a vacumn leak. I think that may solve my air box selection problem. All responses welcome, thanks.
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Unread 03-29-2012, 12:48 AM   #5
Uniblurb
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Good place to start if you're hearing the noise coming from behind the glove box. The main small black vacuum line which feeds the HVAC vent control comes through the firewall next to one of the AC lines and bends over to the control area behind the glove box. It may also be clipped to the front of the AC evaporator/heater core plastic housing box in that location.

You should just be able to take the lower part of the plastic dash off/lose (from door jam to where dash sticks out) and the glove box out to get to it.

There's also a blend door actuator, with a vacuum line running to it, clear down under the dash on the far right side next to the floor/firewall. Believe there's three 8mm headed screws holding this plastic cover on above the fuse box. You may want to check this vacuum line for leaks too but this blend door doesn't have anything to do with changing defrost to floor vents.

Good luck.
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Unread 03-29-2012, 10:16 AM   #6
BenHoleton
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Quote:
Originally Posted by sebian View Post
Or, if you are not a cigar smoker, start looking at the vac lines on the intake manifold. After 15 years, they tend to get a little brittle and start cracking and breaking. There is also a vac line that runs under the battery tray. That one is pretty notorious for leaking.
Why would you not be a cigar smoker?

Last edited by BenHoleton; 03-29-2012 at 10:16 AM.. Reason: typo
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Unread 03-29-2012, 07:49 PM   #7
mlhelfin
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Quote:
Originally Posted by Uniblurb View Post
Good place to start if you're hearing the noise coming from behind the glove box. The main small black vacuum line which feeds the HVAC vent control comes through the firewall next to one of the AC lines and bends over to the control area behind the glove box. It may also be clipped to the front of the AC evaporator/heater core plastic housing box in that location.

You should just be able to take the lower part of the plastic dash off/lose (from door jam to where dash sticks out) and the glove box out to get to it.

There's also a blend door actuator, with a vacuum line running to it, clear down under the dash on the far right side next to the floor/firewall. Believe there's three 8mm headed screws holding this plastic cover on above the fuse box. You may want to check this vacuum line for leaks too but this blend door doesn't have anything to do with changing defrost to floor vents.

Good luck.
Okay fine UNIBLURB, sounds like you've been there. It's definately in that area. I probably need to start under the battery tray and work my way back. That line running through the firewall into the interior looks like it might be an 1/8" line. Is that the one running my HVAC controls ?
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Unread 03-29-2012, 10:28 PM   #8
Uniblurb
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Quote:
Originally Posted by mlhelfin View Post
Okay fine UNIBLURB, sounds like you've been there. It's definately in that area. I probably need to start under the battery tray and work my way back. That line running through the firewall into the interior looks like it might be an 1/8" line. Is that the one running my HVAC controls ?
Don't know if the 95 is exactly the same as a 96 but since my ZJ was built late 95 I bet it is. Yeah, have had to replace the AC evaporators/heater cores in my ZJ, and wife's TJ, so kind of familiar with what's behind he dash. Also have had to repair a vaccum leak in the same area you're talking about.

I would start where you hear the leak instead of tracing the whole line. There's a vaccum line going across the top part of the outside firewall with a "T" in it. The main black (yeah, 1/8") plastic line T's off and goes through the firewall next to the line. This is the main feed for the whole control knob. And as mentioned before it turns towards the control unit behind the left part of the glovebox opening.

About all you need to do is look under the bottom part of the dash and start taking screws out. Try to just take the ones out which are holding the plastic dash on and not the ones holding the metal part of the dash to the metal framing. I use an electric drill for this type of work since there's quite a few screws. But you can't get to them all using a drill. Also there's some holding the glove box in. There's a phillips screw over by the door jam you need to use a short phillips on with the door all the way open. You'll probably also have to pry out slightly on the plastic part of the dash to get some of the metal clips to break loose. The lower half of the plastic dash may not want to detach itself from the left side where the dash stick out. But it will be loose enough where you can work around it. There may also be some vent tubes you will have to move out of the way or disconnect.

I've also taken out the whole HVAC control unit part way out of the front of the dash many times. You can only pull it out so far because the vacuum/electric lines don't have enough slack in them. There's only about 3-4 screws holding the trim/front around this (along with radio) and the rest are all clips. There's a screw hidden behind the ashtray and you need to remove it to get to it. You may not even need to go there if you find the leak behind the glove box and repair it.

Most say to disconnect the battery before even starting to remove dash parts in this area. The air bag is right behind the dash above the glove box. I'll typically disconnect the battery a couple hours before starting to remove dash parts since supposedly the air bag may hold a charge. But once you get the glove box removed you will need to connect the battery/start it to find the vacuum leak. Once repaired it's a good idea to disconnect the battery again before you start hitting the dash parts to snap the clips back in.

Good luck and shout if you need any other info.

edit: I should mention, what do you splice a broken/cracked vacuum line with? Most say you should replace all the vacuum lines if brittle. But if you don't know what you're doing this may not be the best route especially when you get into the back of the vacuum line switch.

My vacuum lines weren't all that brittle and the auto parts stores didn't sell a coupling that small for those tiny vacuum lines. While maybe sounding like a rig-job I took an old Bic pen, broke it, and used a short empty section of the tube which holds the ink. It fit tight right into the inside of the lines and then put a good electrical tape (Scotch 33) on the outside with the lines butted together. Make sure you use a sharp razor knife when cutting the lines/tubes or you will crimp them if using sidecuts/dikes. Did this repair about 1 1/2 years ago, hasn't leaked since, and the ink tube does not restrict the vacuum since all my blend doors work great.
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Unread 03-30-2012, 07:33 PM   #9
mlhelfin
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Thanks Uniblurb. That's just what I was looking to hear. I know the 1/8" line under the firewall coming out of the T your talking about. We're on the same page, now I just got to get in there and fix it. Really appreciate your input. Mark
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Unread 03-30-2012, 08:00 PM   #10
Uniblurb
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YW Mark, it's not really that hard of a fix and just takes some patience. Believe I may have heated the vacuum lines just slightly with a lighter at a distance to get them soft enough to insert the 1/2" section of tube.

I'm sure you can handle it, let us know how it goes, and good luck.

BTW, those cup holders are great for holding screws and at least they're good for something! LOL.
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