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Need Help Locating a Vac/Intake Leak!!


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Well...I can tell it's coming form somewhere around the intake on the passenger side as it swoops down into the rectangle-ish valve cover.

- What are some ways to locate it exactly? Or more accurately?? I'm stumped.

Is there a common location on '91 Legacy's that have this problem...It's causing all kinds of idle problems....Thanks for the help!@

Jrodan

P.S. Pictures would REALLY help me out too...I don't have a manual...and I'm a little to broke at the momment to buy one for $16-20!!

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get a can of starting fluid or whatever people recommend and use the long piece that comes with the can, looks like a thin straw. use that to direct the spray while the engine is running. when it hits the leak the engine will rev and sputter.

 

i saw a guy at the shop i take my stuff to get inspected with the exact same car and issue. pretty sure it was an intake manifold gasket leak. but each instance can be something different.

 

just get a can, start spraying and ask if you have any questions. won't learn until you try it. it's really simple, point and push the button.

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There's another method besides the "spray" approach that often works. A piece of automotive vacuum hose (not the one from your Hoover :) ) or similar small-diameter tubing of appropriate length is used; one open end is held to an ear, the other end moved around as close as possible to the area of the suspected leak. A "rushing" or "whistling" sound is heard when approaching the leak, louder the nearer the tube is to the leak. Of course, if you can borrow a stethoscope (minus any solid diaphragm and perhaps even a belled end), that would probably be easier to use.

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The mechanic I have been using for 4 years told me I dont have a vaccum leak, but he cant fix my low idle problem and I have been through USMB threads for months looking for an answer to the erratic low idle. Is it possible he missed something and there is a leak. I do alot of my own maintenance myself but I dont know exactly where to spray water or starting fluid to check for a leak? Any help would be great.

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Sounds like I have some info to help get me started on this problem!! Thanks for the advise!! I have one small question though....At work we use this fake smoke to test smoke detectors...I was wondering about spraying that into the intake after the airfilter and seeing if the smoke would leak out...I'm thinking that it would probably work better to not have the car running, as the fan would blow any smoke away from it's point of leakage.....this stuff is made out of "ISO Butane and propane"....Has anyone used anything similar to find leaks???...if not I'll let you know how it works if I need to use it after I try the other ideas....Thanks so much for the help!!

Jordan

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[...]At work we use this fake smoke to test smoke detectors...I was wondering about spraying that into the intake after the airfilter and seeing if the smoke would leak out...I'm thinking that it would probably work better to not have the car running, as the fan would blow any smoke away from it's point of leakage.....this stuff is made out of "ISO Butane and propane"....Has anyone used anything similar to find leaks???[...]

A "vacuum leak" is an unintended opening at the intake side that "leaks" vacuum; in other words, it's a low-pressure area when the engine is running, and will suck in things that are at higher pressure, like atmosphere or a test fluid. So spraying the "fake smoke" into the intake therefore wouldn't be useful with the engine running, since it won't exit at the area of the leak. It possibly won't be evident with the engine off, either, since not much would be propelling it towards the opening. I'd also be concerned about how that gas mixture might affect a running engine. Why not try the other suggestions first?

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  • 4 weeks later...

Ok, I know it's been awhile since I posted this..bvut I tried all the suggestions and the first day I got some results...I was spraying wd-40 near the passenger side intake manifold and the idle changed, but the next day I tried the same thing and got no response....??? Whats involved in taking the intake manifold off and checking the gasket??

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