ESOF problem
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Senior User
Joined: Dec 2006
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From: Henderson, Ia
ESOF problem
Trying to get the esof working again on my truck, but have no vaccum going to the hubs. The pump is working and have vaccum to the heater controls, but when I pull the connection apart going to the hubs I get nothing! The lines run to a device on the fender with an electrical connection, I have vaccum at the red line but not at the black one that goes to the hubs. Any suggestions??
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Joined: Jun 2002
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From: Panama City, Fl
You need to test for vacuum at the time the switch is operated. Have someone select 4 wheel drive while you are at the pump checking for vacuum. I think it is a timed vacuum operation to shift the hubs I to gear....at least that is the way my 7.3 worked.
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I'm having issue with my 4x4 as we'll. I'm stumped man. My truck is 4wd. I put it in 4wd, indicator lights up I hear it sound like it's in. I go and nope still only rear wheels. So I get out and manually lock the hubs. Get back in and still only 2wd. So I get out the front driveshaft won't spin. Cool my t case is working. I go and turn each knuckle behind bOth front wheels and they won't turn which tells me hubs are locked in. But wtf my 4wd won't work?? Iv went forward backwards 4h 4L. I just am confused?
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There areseveral good write ups concerning this on the Forums and YouTube. I am a fan of guzzle's 2002 Ford Powerstroke Diesel Auto Lock Hub Disassembly and Lube among others for an in-depth analysis of the inner workings of the Hub<o
></o>My comments(whatever they’re worth) is that the ESOF System operates by Electric Switchwhich when moved on the dash results in the PCM commanding the vacuum solenoid anddisplays on the on the instrument panel. MOMENTAY VACCUM PULSE to the Hubs movinga disc which allows the opposing gears to engage. Periodic maintenance on thehubs is a MUST to ensure seals and O-Rings remain pliable and "AirTight" in order to function when needed.<o
></o>Whenever the front wheel hubaxle shaft or the hub lock is removed and installed, the front wheel-endassemblies must be leak-checked to ensure that the sealing surfaces are intact.Failure to do so can cause the loss of four-wheel drive operation andcontamination of the vacuum system.
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></o>Disconnect the wheel-end vacuumhose. Connect the hand vacuum pump (part of Vacuum Tester) to the vacuumfitting on the wheel knuckle. The wheel-end assembly must not leak more than0.50 in-Hg in 30 seconds. If the wheel-end leak rate exceeds the specification,refer to Transfer Case Testing and Inspection under Transmission andDrivetrain. Apply 15 in-Hg of vacuum to the wheel-end assembly and observe thereading for 30 seconds.
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></o>Repeat the leak testingprocedure for the opposite wheel-end. When the 4x4is engaged, a vacuum solenoid is actuated allowing a negative pressure in thehub for only a few seconds thereby engaging the Hubs. As well, the electricshift solenoid on the transfer case receives its signal from the vacuum aswell, engaging the lock pin which marries the transfer case gears. Hence, avacuum line damaged or deteriorated anywhere in the system can cause a failureof one or both Hubs as well as the Transfer Switch to operate.<o
></o><o
></o>One way Ihave found as a LAST RESORT (through trial and error)over the years is to pressurize the vacuum system to about 5 lbs. using an airregulator and spraying soapy water on the lines and hubs until I see bubbles orhear air escaping from a damaged or broken line, defective seal or O-Ring. <o
></o>The ESOF ElectricTransfer Valve can be tested ***WITH THE KEY OUT OF THE IGNITION*** (gets a groundsignal from PCM) putting 12VDC momentary and listen for the solenoid to move.This is a MOMENTARY circuit, no more than a SECOND seconds at a time. APowerProbe III works great for this purpose and can also cheek the groundactivity from the PCM with KOEO. ***DO NOT ENERGIZE THE POWERPROBE! ***.Just look for the green (-) on its display when someone else moves the switchthrough its three positions. The same can be accomplished with a quality DVOMset on OHM.<o
></o>I do ALL 4x4Maintenance in July. I have never had an issue since a failure in January in afoot or two of snow which taught me a very useful lesson: 4 wheel drive isn’tworth a fart if it don’t work!<o
></o>Specialnotes:<o
></o>**WITH THEKEY OUT OF THE IGNITION** IF YOU HAVE A DOUBT, THROW THEM IN THE WOODS. THEY’LLBE EASIER TO FIND THAN THE $800 FOR A NEW PCM!<o
></o>***DO NOTENERGIZE THE POWERPROBE! *** IF YOU ENEGIZE THE POWERPROBE I’LL HUNT YOU DOWNAND BEAT THE CRAP OUT OF YOUR STUPID BUTT! <o
></o>LAST RESORTMEANS AFTER YOU HAVE THROWN ALL YOUR TOOLS AND KICKED YOUR CAT AND DON’T HAVEANY ADULT BEVERAGES LEFT IN THE REFER.<o
></o>Hope thishelps.<o
></o>Tom<o
></o>
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