2004 WJ 4.0 Inline 6 CC/AC Problems - JeepForum.com
 
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post #1 of 8 Old 07-01-2013, 01:47 PM Thread Starter
michaelgoggins
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Wj 2004 WJ 4.0 Inline 6 CC/AC Problems

I have an 04 WJ with an apparently common problem with the Vac line for the the cruise control not working and the HVAC only blowing to windshield. I have seen posts on how to fix it, but I need some visual examples. If anyone has any pictures that they can post of this fix it would be greatly appreciated.

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post #2 of 8 Old 07-01-2013, 05:32 PM
338WinMag
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cykaaro quotes :

If you pull off the lower bezel and upper bezel around the radio, you'll be left with the HVAC controls, which are held in by 4 screws. You can take the screws out, and pull the unit out. The settings where it blows is done by way of vacuum lines. Most issues with that are due to if it's taken out and disconnected, and not seated right putting it back on, can give problems. There's one main feed line to it, black I think, which goes to it through the firewall. I've seen on vehicles where that can be an issue if there's a vacuum leak happening. May not be the issue, but good place to start. Then work your way from there.

I'm thinking it sounds like as the motor is creating more of a vacuum at higher RPM's, it's causing to leak somehow, maybe a small hole or crack, which then causes a vacuum loss and then everything goes through the defrost, which is the default, as without vacuum, whatever setting you want will now not work.
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post #3 of 8 Old 07-01-2013, 10:31 PM
rdkendrick
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Quote:
Originally Posted by 338WinMag View Post
cykaaro quotes :

If you pull off the lower bezel and upper bezel around the radio, you'll be left with the HVAC controls, which are held in by 4 screws. You can take the screws out, and pull the unit out. The settings where it blows is done by way of vacuum lines. Most issues with that are due to if it's taken out and disconnected, and not seated right putting it back on, can give problems. There's one main feed line to it, black I think, which goes to it through the firewall. I've seen on vehicles where that can be an issue if there's a vacuum leak happening. May not be the issue, but good place to start. Then work your way from there.

I'm thinking it sounds like as the motor is creating more of a vacuum at higher RPM's, it's causing to leak somehow, maybe a small hole or crack, which then causes a vacuum loss and then everything goes through the defrost, which is the default, as without vacuum, whatever setting you want will now not work.
Most of the posts that I have read about the 4.0 L, the fix was a dry rotted vacuum line running under the battery holder.

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post #4 of 8 Old 07-02-2013, 09:31 AM
doityourselfMM
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Having this exact problem with the Wife's '04. I traced the problem to the vacuum box itself, and a leak. Since I have to pull the front bumper fascia, both headlights, and the headlight mounting panel, I will replace both the vacuum accumulator and the hose assembly that runs from the intake manifold, across the top of the firewall, down under the battery, and 'Ts' to the Cruise Control Actuator and the Vacuum Accumulator. Total in parts ... $33.00!

I borrowed this image from another thread, credit to joeisalsocool. I will remove if there is a problem. The image shows exactly the area beneath the battery, the cruise actuator, the rubber lines, the 'T', and the vacuum accumulator. Great photo for reference!

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Originally Posted by 338WinMag View Post
cykaaro quotes :

I'm thinking it sounds like as the motor is creating more of a vacuum at higher RPM's, it's causing to leak somehow, maybe a small hole or crack, which then causes a vacuum loss and then everything goes through the defrost, which is the default, as without vacuum, whatever setting you want will now not work.
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post #5 of 8 Old 07-04-2013, 02:10 AM
cykaaro
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Don't you love how everything is so nicely and neatly buried when you want to work on it? A lot of vacuum issues just seem to be old lines needing to be replaced. Of course except in my case. Mine was some asshat put the check valve the wrong way.

The beatings will continue until attitudes improve!

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http://www.hidplanet.com/forums/showthread.php?44572-Jeep-2000-Grand-Cherokee-WJ
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post #6 of 8 Old 07-05-2013, 08:49 AM
doityourselfMM
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The way 'they' build vehicles reminds me of packing a suitcase. You start out with a basic rectangle, and see how much 'stuff' you can fit inside. Of course, the underwear and toothbrush are always packed in the bottom, where you can't find them, so everything else needs to be unpacked. I know, stupid analogy.

Interestingly enough, the new vacuum harness (from the intake manifold back to the 'T' by the cruise actuator and vacuum accumulator) is now all semi-flexible plastic. Maybe acid resistant so the battery overflow doesn't melt it.

And guess what explodes during any front end impact? The plastic vacuum reservoir! The least of one's worries, I guess...
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post #7 of 8 Old 07-05-2013, 12:13 PM
cykaaro
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I remember the old round one on my XJ getting nailed. Just relocated it up into the engine bay. Problem sovled. Oh yeah. Then I got a WARN bumper.

The beatings will continue until attitudes improve!

HID Quad bi-xenon + foglight retrofit
http://www.hidplanet.com/forums/showthread.php?44572-Jeep-2000-Grand-Cherokee-WJ
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post #8 of 8 Old 07-07-2013, 01:01 AM Thread Starter
michaelgoggins
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Wj its fixed!

I took the passenger head light out and checked the hosing behind it and it was dry rotted so I replaced it with new hose and now it works perfectly. Thanks for all the replies guys.
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