Figured out my ESOF problem - Ford Powerstroke Diesel Forum
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post #1 of 2 Old 03-18-2012, 02:23 PM Thread Starter Fanatic
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Figured out my ESOF problem

I finally figured it out why my ESOF was not working. I took multiple searches from three different websites and put them all together to figure it out. I didn't use any gauges or vacuum pumps.

Initial indications were she just wouldn't shift. The 4x4 light would come on but it would not be in 4x4. No vent to defrost issues. (that comes in a bit)

Checked all of the associated fuses. Checked good.

My vacuum pump ran fine with the key on.

First unhooked outlet hose from the pump. Vacuum pressure felt good.

Unhooked the outlet from the reservoir. Vaccuum pressure felt good.

Unhooked the hose that comes out of the solenoid and turned on the 4wd. Nothing. Checked the power to the plug with a multimeter and it checked good.

So I took the solenoid off and took off the top cover. Took off the filter and put some air tool oil in the small pistons. Put her back together and the vacuum pressure was good.

Still no 4wd. Now when I hit the switch my vent would go straight to defrost. Hmmmm. Now I know I have a pressure leak in the system.

Took a trip to Lowes and bought 8 feet of 3/16 inch ID hose ($8). Replaced all of the rubber hose under the truck. Tried the 4wd again. It wouldn't shift and now my vent very slowly went from vent to defrost. Getting better so I knew I fixed a leak.

Isolated the hubs by unhooking each side one at a time and putting a piece of tape over the disconnected hose. With the passenger side blocked it still slowly went to defrost. When I blocked the drivers side she worked great. Driver's side was the culprit.

Took out both hubs and lubed with bearing grease. Put everything back together and it the 4wd works 4.0.

Ended up with three problems.

1. Solenoid on passenger side behind battery was stuck closed.
2. Had a hole in the tubing under the truck
3. Hubs had been neglected and needed some love.

2006 F-250 CC Lariat FX4
Dieselsite coolant Filter
AFE intake
Edge Insight CS
Edge pyro
FP sensor
Edge turbo timer
CAT EC-1 rated ELC
blue spring upgrade
Aluminum cold side CAC
Bilstein HD shocks
Bilstein steering stabilizer

Last edited by arbarlow; 03-18-2012 at 06:08 PM.
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yamasaki (08-15-2014)
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post #2 of 2 Old 08-15-2014, 10:49 AM
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Excellent. My ESOF is inop as well. I have to do the walk of shame down to the hubs when i want 4WD.

My friends with $45,000+ trucks and $800/mos car payments laugh at this procedure.

I look forward to correcting the problem with a few singles (maybe a $20) and laughing back at them for a few years.


2007 6.0 CC FX4 Lariat

Insight CTS, SCT 3015, EGR Delete, 4" TB Exhaust w/hollowed cat, ARP studs, OEM HG, Coolant Filter, BPD Water Pump, K&N CAI, King Ranch interior, Pioneer AVIC x910bt, Nitto Terra Grapplers
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