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possible vacuum leak


Old 05-01-2008, 06:41 PM
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possible vacuum leak

2000 F150 5.4l 87,000 miles. I believe i have a vacuum leak but am not really sure and need to locate it. I have a consistent beeping sound when my truck is in R,D,1 or 2. It is only audible with my foot off of the throttle. This includes 55mph if i just let off and let it coast. It is also audible for a second when the truck is put in park and then shut off. It has been a month or so and have yet to throw a code. I had a loping idle about 2 weeks ago but have not noticed that since then. Is it a vacuum leak, if it is where??

Also i believe i have bad valve stem seals due to blue smoke on startup. (not sure if that has anything to do with it.) I'm 17 and would like to learn something and also have a chilton manual.
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Old 05-01-2008, 07:38 PM
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The most common places for vacuum leaks are the PCV elbow behind the throttle body, and the lines that run behind the battery.
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Old 05-01-2008, 08:04 PM
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ok. does it sound like a vacuum leak? Should i try to find it myself? How? soapy water mixture?? or just take it to my mechanic and have him use the Black light or whatever they use?
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Old 05-01-2008, 08:54 PM
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I've seen some BLEEPING vacuum leaks but never a BEEPING vacuum leak. Where does the beeping sound like it comes from? Behind the dash maybe? Does your air bag light illuminate when you switch the truck on?? If the bulb is burned out it will beep at you.
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Old 05-01-2008, 09:00 PM
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not an airbag light. i just went and checked and both lights came on. i was really hoping it would be something simple like that. what should i check/do next?

shouldn't it be something specific seeing as how it only happens in gear and no throttle?? maybe not. BTW its not exactly a beeping sound maybe more of a consistent squealing sound. Quite faint but indeed audible.

Last edited by cookdawg06; 05-01-2008 at 09:03 PM.
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Old 05-02-2008, 03:46 PM
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please do not use soapy water to find a vac leak if you find one then you will have soap and water in your engine not good use something like wd 40 as that will burn in the engine and not cause damage if you find a leak the engine should speed up a bit or smooth out then you'll know where your leak is

Last edited by po1911; 05-02-2008 at 03:49 PM.
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Old 05-02-2008, 04:17 PM
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lol yea. soapy water was my first reaction because thats what we use on AC units at work. then i thought about the engine sucking in soapy water and not even making bubbles. Read the wd 40 or carb spray trick online somewhere and using soapy water whilst pressurizing the system. Just out of curiosity does anyone know if the smoke systems are used with the vehicle on or off? If its on wouldn't the vac system suck air in the hole and not let the smoke out? But if its off wouldn't the valves be closed??
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