Good Ways To Check Vaccum Leak - Taurus Car Club of America : Ford Taurus Forum
 
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post #1 of 8 (permalink) Old 03-05-2010, 11:44 AM Thread Starter
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I suspect there is a vaccum leak somewhere and I need to find it out since the car has rough idle lately. After searching the forum, I have yet seen a recommended way of doing it. Could somebody please shed some light on this?

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post #2 of 8 (permalink) Old 03-05-2010, 12:14 PM
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the most common ways of doing it are spraying carb cleaner around areas you think the leaks are. When the idle changes you know you've found the spot.

The other way is using propane gas instead of the carb cleaner. I've never trusted this way though. Seems a little too dangerous to me to be pumping flammable gas into a car that uses sparks to run.
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post #3 of 8 (permalink) Old 03-05-2010, 12:14 PM
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easiest way is to spray some carb cleaner around the intake and all the vacuum hoses. if the engine smooths out then you have found your leak. just dont spray it directly on the exhaust.
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post #4 of 8 (permalink) Old 03-05-2010, 12:23 PM
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QUOTE (batrachian @ Mar 5 2010, 12:44 PM)
Quote:
I suspect there is a vaccum leak somewhere and I need to find it out since the car has rough idle lately. After searching the forum, I have yet seen a recommended way of doing it. Could somebody please shed some light on this?[/b]
Do a search for codes P0171 and P0174. If you have a vacuum leak bad enough to cause idling problems you should have a CEL. If so follow the write ups for those codes. Usually 3 or 4 ways to find a vacuum leak. One visually check all rubber hoses for cracks, especially those going to and around the PCV. Two disconnect and cap the main vacuum source from the engine to the vacuum box on the firewall. If the engine then runs good your vacuum leak is in other areas than the engine, such as EVAPS, brake booster, or all your heating and airconditioning controls (DO NOT DRIVE YOUR CAR WITH THIS LINE CAPPED OFF< YOU WILL NOT HAVE BRAKES). Next you can use spray starter fluid, spray brake cleaner, or propane and spray around hoses, upper and lower intake, etc. If engine runs better when you get to a certain area you have found your leak. For those who get those codes but really do not notice any performance issues it gets a little harder. If you have a engine code reader that has the Live Data function you can monitor the Short Term Fuel Trim Levels as you spray around the engine. If you get near a leak the levels should move closer to zero or go lower. For your rough idle also check the operation of your EGR system. If you are really sure you have a vacuum leak and can't find it, you can go to a garage that has a smoke machine that will find it rather quickly. Hope this helps.

ED
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post #5 of 8 (permalink) Old 03-05-2010, 12:29 PM
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after reading that article about carb cleaner fumes and the guy almost dying from a "pfft" minute poof of those fumes, I'll use propane thanks.

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post #6 of 8 (permalink) Old 03-06-2010, 08:11 AM
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I do NOT recommend using flammable items to test for vacuum leaks. A good way to end up like me....Bald....although mine is natural.

Use either an engine stethescope, or a length of small hose. Stethescopes are better as it shuts out ALL (almost all) outside noise. A hose to the ear also works, but not as good. When you find a leak, it is a sucking noise and when you find a big leak, it sounds like a freight train going by. Run the hose around all parts of the intake manifold and ALL hoses...especially under the intake manifold around on the right side and anything on the firewall. It should take you about 15 minutes to check everything. The infamous ELBOW leak is usually located under the Intake upper manifold and you need to pay special attention, running the hose all around under the throttle area to check these hoses. For those with DOHC engines also run the hose under the intake manifold down in the 'valley' of the engine where the PVC is located. The EGR valve should also be checked this way. NOTE: If you have had the car for four years or have never done so, remove the EGR valve and check its operation. You would be surprised at what you may find in it and its tubing.
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post #7 of 8 (permalink) Old 03-06-2010, 09:07 PM
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Another thing is you can actually use a vaccum gauge. The only issue is if the vaccum leak is small, it would be hard to know what's normal and what is not...
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post #8 of 8 (permalink) Old 03-06-2010, 09:35 PM
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with a gauge you should probably get somewhere around 20 in. of vacuum.......round-about, if it's a well running engine.

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