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Discussion Starter #1
Up until recently my ESOF hubs have been working fine (2000 F250 7.3 218K miles), though I don't often have occasion to use the 4wd in Ohio. Now recently they won't engage automatically. Manual engagement is fine. It would seem to me that if it was a vacuum line to the hub only one side would fail (the one with the bad line)? So maybe its the solenoid that failed? But the heater controls work fine. What should I be looking for and how do I diagnose.
Before I get too many comments, I know that most people like to put manual hubs on and toss the OEM hubs. If I were a serious off-raoder that would make sense. But I'm not. I like the convenience of having 4wd on demand without having to turn all the axles/bearings/gears 99.5% of my driving hours. Should save fuel as well as wear and tear. Bottom line, I want to keep the ESOF hubs even if I have to rebuild or replace them. Heck, they've gone 218K on the first set. If I get 200K out of another set that should do me.
 

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The vacuum-operated thing probably failed, or your luck just ran out on the hubs in general. I think I put two of the vacuum switch things on my '99 in only about 135,000 miles. Best advice, forget the hubs are automatic and use them like manual hubs. If your heater goes nuts, pull the line to the switch thing and put a pen cap in it to block it.
 

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Discussion Starter #3
I apologize if this is a repeat. I thought I posted it 2 days ago but don't see it anywhere (I'm new here).

My ESOF has been working fine until recently but went to use it this week and the hubs don't lock. I can manually lock them, and did, and was able to use the 4wd many times this week as my road is flooded. Seems like if it was a vacuum line leak it would only affect one side? Might it be the solenoid? How do I check? Please use few acronyms as possible as this is my first diesel (2000 F250 7.3 200K). Also, I like the auto hubs and am not a serious off-roader so want to keep them. Better fuel mileage and less wear/tear on drive train. Thanks
 

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Think of the hublocks as click type ball point pens. Push them on with a vacuum pulse, push them off with another. The solenoid provides 15 inches of vacuum to apply and 7 inches to unapply. Any leak will stop operation of both hublocks as they are tied together. Lines, vacuum hub seal failure due to bad ball joints, wheel bearing failure, solenoid failure, hublock failure of their vacuum diaphragm, torn hublock or wheel bearing o rings, vacuum pump failure.... the list goes on. Buy a handheld vacuum pump with guage. disconnect the lines at the solenoid. Check for adequate source vacuum once the pump turns off- over 15 inches Hg. If that is fine, put the source vacuum back on the solenoid and the pump gage on the outlet of the solenoid. Check for 15 inches to apply and release in 4x4 and 7 to apply and release in 2wd. The 4x4 module can hold one on or off till a timer has elapsed, IIRC 2 minutes. If you got good readings there, you have a leak somewhere in the hublocks/bearings/lines. Remove each line at the spindle. block with a golf tee or something of the like. apply hand pump vacuum to check the integrity of the lines. Check each hub with the hand pump. Should hold 15 inches Hg with no leaks. Do this with the wheels off the ground and spin them hublocks engaged and disengaged. You will find your fault eventually.
 

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I apologize if this is a repeat. I thought I posted it 2 days ago but don't see it anywhere (I'm new here).
Merged your two posts, as they both had replies.

Welcome to TheDieselStop. Looks like the guys are giving you some good advice.

klhansen
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Discussion Starter #6
This is great! thank you all for the troubleshooting instructions (and in layman's terms too) and for merging my double post. Now, to get to work!
 
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