AC issues and cruise control problems - JeepForum.com
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post #1 of 17 Old 08-15-2017, 07:38 AM Thread Starter
JimE2
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AC issues and cruise control problems

Ok , I know I must have a vacuum leak some where. First, my AC will blow great out the front vents, then for no good reason, about haft the air will divert on it's own to the defrost. Then cycle back, randomly. Sometimes it seems to be RPM related, other times speed/gear related, but I can't get it to repeat reliably.

I have also noticed that my cruise control is not setting. The light on the dash comes on, but will not set the speed.

I have replaced the vacuum lines from the manifold all the way to the battery side, and these connections seem fine. Could this be a failed check valve issue? Is there a booster, or other gizmo that may be at fault? What am I missing?

Thanks,

Jim



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post #2 of 17 Old 08-15-2017, 07:52 AM
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It's a vacuum leak. Have you checked the line near the T that goes into the firewall? Two of my Jeeps cracked there and caused the same problems. I couldn't see the crack until I twisted the line.

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post #3 of 17 Old 08-16-2017, 01:53 PM Thread Starter
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Thanks for the response. I'll check it out. Are there any test to help sniff out hidden leaks?


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post #4 of 17 Old 08-17-2017, 12:44 AM
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Thanks for the response. I'll check it out. Are there any test to help sniff out hidden leaks?
Not that I know of. Here's a vid of where many tend to crack.

https://www.youtube.com/watch?v=Tuww...I#action=share

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post #5 of 17 Old 08-17-2017, 05:52 AM
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Thanks for the response. I'll check it out. Are there any test to help sniff out hidden leaks?
Smoking may help. A lit cigarette is a useful tool for finding vacuum leaks (and pressure leaks, too). Run it slowly near the lines, and you may be able to see the smoke getting sucked into the leak. However, the radiator fan, wind, etc., may be more powerful than the leak itself, and this test may not work. If you're a hippie, an incense stick can be used instead of a cigarette.
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post #6 of 17 Old 08-17-2017, 07:22 AM
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If you're a hippie, an incense stick can be used instead of a Mary Jane cigarette.
Fixed that for ya.

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post #7 of 17 Old 08-17-2017, 07:26 AM
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Fixed that for ya.
Wouldn't want to waste one of those hunting down a leak.
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post #8 of 17 Old 08-17-2017, 10:28 AM
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I've heard of mechanics using a smoke generator to fill up the system and then visually inspect if you see the smoke leaking out anywhere. The cigarette trick might work the same way. Take a puff, remove the brake booster vaccum line and blow the smoke into the system. I don't know if there are any check valves that might prevent from doing that though. I'm just spitballing an idea out really.
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post #9 of 17 Old 08-17-2017, 12:01 PM
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I've heard of mechanics using a smoke generator to fill up the system and then visually inspect if you see the smoke leaking out anywhere. The cigarette trick might work the same way. Take a puff, remove the brake booster vaccum line and blow the smoke into the system. I don't know if there are any check valves that might prevent from doing that though. I'm just spitballing an idea out really.
Yes, there is at least one check valve in there, in addition to the one on the booster itself.

Not sure if blowing smoke into the system would be helpful. Vacuum leaks tend to be tiny cracks (at least what I've seen). Putting enough smoke and pressure in there to see smoke coming out a crack may blow the crack out and make it worse. On the plus side, though, at least you'd be able to see it.

I remember once on my first submarine, we had a vacuum leak in one of the main condensers. Big enough to see on the gauges, but too small to hear or feel. We invited the smokers to leave the smoke pit (this was back when we were still allowed to smoke on submarines), come and light up in the area, and use their cigarettes to look for the leak. They enjoyed being able to light up in a "forbidden" area, and they quickly found the leak.
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post #10 of 17 Old 09-17-2017, 11:30 AM
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Using hairspray is another technique to finding a vacuum leak. Just spray on the lines and fittings, if the RPM's drop there is where the leak is. Just keep spraying and following the lines until you see the drop.
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post #11 of 17 Old 09-18-2017, 09:44 AM Thread Starter
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Found it. The line going to the cruise control inside the webbing was the culprit.


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post #12 of 17 Old 09-18-2017, 12:27 PM
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had these issues too last week.

Found two lines that were cracked and holy

the only parts store I found that had these lines were @ the dealer. Anyone else find these anywhere BUT the dealer? I have taped up the cracks/hole for now.

Thanks in advance

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post #13 of 17 Old 09-19-2017, 06:37 AM
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I doubt you're going to find any place other than a dealership or online Mopar parts distributor with the preformed hard plastic vacuum lines. You could replace them with rubber vacuum hose though.


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post #14 of 17 Old 09-19-2017, 09:43 AM
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I doubt you're going to find any place other than a dealership or online Mopar parts distributor with the preformed hard plastic vacuum lines. You could replace them with rubber vacuum hose though.
yeah I was going that route but the vacuum lines have a bit of a lip (2) to be exact on the ends to hold the lines onto the fittings, rubber ones don't. Looked pretty hokey to me....but I guess so does electrical tape to cover the holes... For now its good with the tape.

I will check our Jeep wrecker out this week and see what they have

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post #15 of 17 Old 09-19-2017, 09:49 AM
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A small zip tie used as a "hose clamp" looks just a little better and won't peel off.


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