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Discussion Starter #1
Are there any? I can hear a vacuum leak when I'm driving, especially when it's cold out. I can't quite pinpoint where it might be coming from, but are there any common places to check?
 

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Would love to hear ideas on this too...... I'm not the daily driver of this 01 Laredo.. but I have heard this intermittant whistle... only when moving.. and would kick in @ 15-20 mph. Then magically ... no noise. Then it would come back on another day....
It is not related to RPM's or does not appear to be since no noise standing still @ idle... and will not appear with increase rev's. Only in gear at speed...and not every day.:confused:
 

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Discussion Starter #3
That's odd. Mine is definitely associated with engine speed. It seems to be the worst in the 2-3k RPM range.
 

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I've heard of guys using starter fluid/brake cleaner sprayed (short burst) around the vac lines while running to find the leak. Listen for the surge, there's your leak.

Sam
 

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Discussion Starter #5
I'm pretty sure I found mine this morning. It's the line that goes from the evap control module (if that's what it's called) to the throttle body. It's leaking at the throttle body end. I'm probably going to take it to a local guy to have him swap it out for me. I figure it can't cost too much and I don't have the skin left on my finger tips still from doing the lift in the cold to start another outside, cold project.
 

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x2 on using the spray cleaner to find a leak. But that would be on hoses on/to the throttle body I think. Seems to be fewer hoses/lines these days as compared to years ago...

With mine... been too cold to check further... and due to the intermittant nature. I was thinkin maybe the evap system??? or something with the transfer case??? Is there not an open line there? Not too sure yet how that all works.

A "new" owner gaining knowlege..... thanks to the fine folks 'round here!
 

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Discussion Starter #8
Mine was the vacuum line going to the evap control module or whatever it's called from the throttle body. I went to my local guy and told him where the leak was and he fixed it for nothing. That was pretty nice of him. I didn't have to sit outside in the cold and mess with it, nor did I have to go and spend any money on any vacuum lines. It's idling much smoother. Now I have to wait to start it up when the engine is cold and double check for that "hissing" sound to make sure there aren't any other leaks.
 

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I had a leak that was bad enough to throw a CEL back last month, happened right before I went out of town for 2.5 weeks for the holidays. Spent some time reading about the evap system and how I'd have to pull the rear bumper off because most of the components are back there near the gas tank.

I'm glad I didn't listen to that advice. When I got back I opened the hood and checked all the vacuum lines I could see...and BINGO. There was one (3/8" line) on the bottom of the evap system's charcoal canister (mounted kinda near the brake master cylinder) and the hose was split right in two at that nipple. I didn't have any hose to fix it, so I cobbed together a fix using some tubing I did have laying around, reset the CEL and told the wife "if you see it come back on, let me know." Almost a week now and nothing...so I think it's licked. Good luck to all with similar problems!
 

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Discussion Starter #10
Man, I didn't know that most of the evap system was near the gas tank and that the rear bumper would have to come off to work on it. Hopefully I don't run into any problems like that.
 

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Not sure about the ZJ but it sure is on the WJ. A royal pain. Give a good look in the engine compartment to see what you can see. Good luck!!
 

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Discussion Starter #13
Out of curiosity, how much did you pay for a new canister?
 

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Discussion Starter #15
Ha, if it works, use it! Nice. I've been dying to go to my local Pick N Pull for a while now. It's just cold here and I don't know if it's worth the dollar to freeze my @$$ off to maybe find something worth buying.
 

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Discussion Starter #17
As far as I know, it's right behind the airbox on the 5.2L. It seems to be super easy to swap, if need be. Unless that's not the canister that's there. Regardless, I had the bumper off before when I was putting my tow hooks on so I know how that comes off. I don't think I'll need to be changing it though. I've been idling a lot better now that I got that one line fixed, my acceleration isn't as sluggish, and I'll have to see about my MPGs, but I think they've probably gone up a little, too (making the assumption that I've driven farther on a quarter tank of gas than before. I'll see at my next fill up.)
 
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