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Old 09-19-2011, 10:57 PM
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VACUUM LEAK!! Help Please

Hi all, I have a vacuum leak somewhere, and it's causing my ac not to blow correctly. Also, sometimes my jeep sounds rough, and other times it sounds and feels quiet and smooth. The rough sound and feel happen independently of the A/C problem. I've read about the AC problem and know I have a vacuum leak for sure. How much should I pay for a smoke test/vacuum test at a jeep shop? Thanks for any help.

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Old 09-19-2011, 11:16 PM   #2
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Here I am with my typical diagram I like to spam around! lol

Usually look at where the number 5 port is on the intake manifold(below the throttle body) cause the number 2 90 degree vacuum port loosens and falls off. You can reattch it then put a ziptie around it to make it more secure, or replace it.

If thats not the area then I would look under the battery at the number 8 postion. Easiest way to check it would be to lay underneath and look up right behind the front tire passenger side and it should be sticking out of the lower firewall/frame


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Old 09-20-2011, 02:34 PM   #3
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What he said... I had that problem on my 3,200 mile trip to Ohio through 8 states, which I just got back from yesterday. When you buy the vacuum harness from the dealer, it should be $13 that gets you the vacuum line with the boots that go to the vacuum nipple on the motor, on the speed control sensor, and the AC vent control system.

It does several things: cruise control; AC vent control, and engine idle control.

I just pulled off the assembly at the T and took off the old assembly, and put it in. I'm keeping the rest of the harness in case I have to replace it. You may have to rev the motor up for a while to get the vacuum system set to the correct vacuum spec for everything to work. If you merely put the boot back on without replacing it, you may have AC vent control and cruise control, but you may not have accurate idle control. Replacing said part with a new one fixed the latter problem. I was about halfway through the trip when I fixed it, and I haven't had a problem since.

HOWEVER, if you are a girl/small-handed like me, it's going to be a pain in the arse to pull the parts apart (DO NOT PULL THE BOOT FROM THE PART IT"S ATTACHED TO - it's molded to the connector!) Pull the part off at the T and leave the plastic T with the harness unless you need to replace that as well, but do not try to separate the boot itself from the part it's molded onto.
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Old 09-20-2011, 06:53 PM   #4
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Not sure on the 'smoke/vacuum' test pricing, but whenever I've suspected a vacuum leak, I've always broken out a bottle of carb cleaner, and sprayed it in suspected trouble spots to check for a change in engine speed (obviously, with the engine running). There are numerous spots that can loosen up and cause an unintended vacuum leak.
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Old 09-20-2011, 07:11 PM   #5
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an UNLIT propane torch (the small disposable cylinder type) works well too. Just move the tip of the UNLIT torch around any suspected leak area and it too will change the engine rpm's as it draws it in. The propane smell dissipates in a matter of seconds too which is nice when using it in the interior. Again, and I'm sure I don't need to explain it, DON'T LIGHT THE TORCH ! Believe it or not there are people dumb enough to light it and proceed to wave it around hoses and gasket areas. Got my ass reamed out a few years ago when I told someone about this method because he burned a bunch of hoses and a few wires trying to do it.
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Old 09-21-2011, 02:34 AM
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Heys guys thanks for all the help, I found the leak. It was the vacuum line that connects under the battery tray. The diagram really helped, thanks. Is there any way to clean the whole vacuum system? A spray maybe?
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Old 09-21-2011, 10:01 AM   #7
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What are you cleaning out of the system?
Anything that got sucked into it most likely has already gone through the intake and out the tail pipe.

I guess if you are a glutton for punishment you could do it. Have to pull all the lines under the hood, along with the reservoir, then the half dozen or so lines under the dash, all the vacuum operated motors, and the switch.

Flush them with soapy water, fresh water, then dry em with compressed air.

Not my idea of a fun weekend.
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Old 09-21-2011, 10:51 AM   #8
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You can also just replace them. The grime and heat just aren't very kind to flexible hoses. Not sure how much the kit is on a TJ, but on an XJ you can get them for around 100.
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Old 10-10-2014, 03:34 PM   #9
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bringing this back from the dead but i have the same problem as op and I found the line under the battery completely eaten through. i changed all the lines and connectors from the vacuum box the the manifold just to change them out and my ac still blows through the defroster vent only
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Old 10-10-2014, 06:25 PM   #10
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Quote:
Originally Posted by kylekae View Post
bringing this back from the dead but i have the same problem as op and I found the line under the battery completely eaten through. i changed all the lines and connectors from the vacuum box the the manifold just to change them out and my ac still blows through the defroster vent only
Did you just fire it up and test it then shut down or did you let your Jeep run a lil first?
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Old 10-12-2014, 02:47 AM   #11
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Yes, I let the system pressurize again and drove it for a couple days now and still the ac is only coming out the defroster vents
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Old 10-18-2014, 12:31 AM   #12
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Bump.
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Old 10-28-2014, 08:20 PM   #13
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Bump, need help
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Old 10-28-2014, 08:35 PM   #14
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If you're sure your vacuum is straight check your actuators/blend door.
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Old 10-29-2014, 05:15 PM   #15
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Where's that, the ac and heat works it just only comes out the defroster on all settings.
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Old 10-29-2014, 08:06 PM   #16
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look up under the dash for the actuators, I'll try to get a picture later when I'm near my pc.

have you by chance checked the knob? Is it real easy to turn or does it have some resistance, if it's easy they sometimes crack and when you turn them, you aren't actually turning the switch. Pull it straight off and look at the back.
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Old 10-31-2014, 04:34 PM   #17
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Also noticed that there is a Constant flow of air coming out of the defroster and depending on what the temperature setting is, air comes out that temperature even with the HVAC switch in the off position.
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Old 11-12-2014, 06:12 PM   #18
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Old 11-17-2014, 10:10 AM   #19
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Look at the diagram at the top and look at #5 on the left side of the motor. You can't just put it back on because the rubber has degraded and won't hold onto the vacuum nipple anymore. It must have PERFECT vacuum in the system, and any leakage from the outside will cause the problems you mentioned. If anything, buy the entire vacuum system and replace the whole thing just to be sure. It's happened again, which means the connector at #5 is only good for 3 years at a time before you have to replace it or zip-tie it. I'm miles from the nearest place that has parts, so, I've zip-tied it back on, and it took about 10 miles to re-establish the vacuum in the system.

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