possible vacuum leak
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Junior Member
Joined: Aug 2011
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possible vacuum leak
i have a 2004 f150 with 131000 miles on it. aorund 50-60 mph during acceleration i start hearing a ch ch ch ch ch (best i can type it 
) noise in the front end. it sounds like the right wheel, then eventually makes it on the left front wheel. sounds like the 4x4 interlock is being kicked in and out very quickly. do i have a vacuum leak somewhere in the 4x4? any ideas?
) noise in the front end. it sounds like the right wheel, then eventually makes it on the left front wheel. sounds like the 4x4 interlock is being kicked in and out very quickly. do i have a vacuum leak somewhere in the 4x4? any ideas?
Last edited by crazycarl6411; Aug 30, 2011 at 08:32 PM.
Technical Article Contributor
Joined: May 2007
Posts: 1,221
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From: St. Louis, MO
Most likely yes. Best thing to do is unplug the lines from the actuators. Plug and seal both when you unplug.
I would run some long vacuum line up to your cab from the side making noise and put a gauge on it. Take off down the road doing the speed it acts up and see what the gauge does. I did the same thing. I ended up having a piece of vacuum line that had a slit rubbed in it. Replaced it in 2 minutes and haven't had an issue since.
I would run some long vacuum line up to your cab from the side making noise and put a gauge on it. Take off down the road doing the speed it acts up and see what the gauge does. I did the same thing. I ended up having a piece of vacuum line that had a slit rubbed in it. Replaced it in 2 minutes and haven't had an issue since.
Senior Member
Joined: Dec 2008
Posts: 105
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From: SE Mich.
just stick a vacum gauge right on the fitting of IWE you think is making noise...pump it up and watch the needle...I had the same problem you described...wound up being just a small hole in the diaphragm...bought a new IWE from the dealer...problem solved...
Senior Member
Joined: Jan 2008
Posts: 124
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From: Johnstown, PA
I had the same problem two weeks ago. I would be cruising down the road and / or up a slight grade with the engine at a constant load, when I would hear a ratcheting type sound or almost an a/c line tapping sound on my front left wheel. I would let off of the gas and it would go away. I did some reading and isolated the problem down to my 4wd system not getting enough vacuum. The major test that i did was when the sound happened, put the truck into 4wd. If the sound stops, you know the problem is in the 4wd system.
Without testing my system, I replaced the IWE Solenoid. It was not the problem. (Dorman #600-400 at Advanced Auto $19.50) I didn't have a vacuume gun, so my buddy looked at it.
My buddy has a vacuum gun and tested it. It was holding pressure. So we jacked up the front end and took the lines off by the hubs and spun the wheels. You wouldn't believe the amount of rust that came out of those hub lines! Now I don't have a problem anymore.
Without testing my system, I replaced the IWE Solenoid. It was not the problem. (Dorman #600-400 at Advanced Auto $19.50) I didn't have a vacuume gun, so my buddy looked at it.
My buddy has a vacuum gun and tested it. It was holding pressure. So we jacked up the front end and took the lines off by the hubs and spun the wheels. You wouldn't believe the amount of rust that came out of those hub lines! Now I don't have a problem anymore.
Senior Member
Joined: May 2005
Posts: 298
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From: highlands ranch, co
there are a LOT of postings here about ford hubs and vacuum leaks.
yes you have a vacuum leak, install a tee before the iwe control valve and run engine with gauge hooked up, it should hold steady over 22lbs vacuum and hold it after eng is shut off.
if it is varying with eng speed - leak
i had a lot of problems with the hard plastic tubing sections and to the vacuum can behind the battery.
there are 3 (i think) check valves to hold vacuum steady during rpm changes
i replaced most of the hard plastic stuff with chemical resistent flexable vacuum line
vacuum holds the hubs dissengaged and releases vacuum to engage
yes you have a vacuum leak, install a tee before the iwe control valve and run engine with gauge hooked up, it should hold steady over 22lbs vacuum and hold it after eng is shut off.
if it is varying with eng speed - leak
i had a lot of problems with the hard plastic tubing sections and to the vacuum can behind the battery.
there are 3 (i think) check valves to hold vacuum steady during rpm changes
i replaced most of the hard plastic stuff with chemical resistent flexable vacuum line
vacuum holds the hubs dissengaged and releases vacuum to engage