Question about the ESOF system

Zmann · Dec 21, 2012

thats a dust seal thats technically not the knuckle the knuckle is on the other side of that

Zmann · Dec 21, 2012

the pulse to lock the hubs is max at 8

but the drop points to checking each side at the knuckle input

Zmann · Dec 21, 2012

also remember you need to work fast to get your vac readings anywhere after the ESOF solenoid because it's just a short time pulse after you flip the ESOF switch

Hublock Operation
With the hublocks in the AUTO position, the 4X4 ESOF system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4X4 modes. A high vacuum level (222 mm [8.75 in] Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4X4 mode, and a lower vacuum level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4X4 control module, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Zmann · Dec 21, 2012

ps they have an updated dust seal that actually goes in the axle tube now for the later models 05ish up

CCRICE · Dec 21, 2012

Zmann said:
ps they have an updated dust seal that actually goes in the axle tube now for the later models 05ish up

This, I just did one of those myself and thought it was the wrong one until parts guy informed me. It's not a big issue to address right now I wouldn't say buy definitely something to take care of.

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Zmann · Dec 21, 2012

My dealer put mine in when doing ball joints under warranty I thought they screwed up LOL

mcdaniel1991 · Dec 21, 2012

Can anyone upload a pic of the t adapter

Lassie · Dec 21, 2012

There is a hose feeding down to the back of the hub. A black rubber vaccuum hose. It fits onto a male fitting on the hub. There is also an electrical cable for the abs prox switch. And a brake line.

Once you find the vaccuum line, follow it up to the top of the wheel well. It will plug into a fitting there. This is where to test the hubs.

A strong pump will typically build up to around 15 in, but for now, just verify the leak points.

It does sound like your pvh is bad so far.

Lassie · Dec 21, 2012

If you find a leak in the hub, and change the knuckle seal, then you can change the dust seal then too... But it will be out again the next time you look!

Look under any front end in any parking lot around, and you'll see a dust seal hanging on the shaft.....Don't let that bother you

Lassie · Dec 21, 2012

mcdaniel1991 said:
Ok I tested the pump ( only pulls 8lbs ) tested canister( it holds the 8lb
) tested pvh (spiked to like 2 and dropped) now this t fitting I can seem to find anywhere

I also found this on my driver side knuckle

If it spiked to 2 and started to drop immediately, it is bad. It should hold for plenty long enough for you to operate the switch yourself, walk around and watch it sit at vaccuum canister pressure for several seconds, then fall quickly to nothing.

Lassie · Dec 21, 2012

Zmann said:
the pulse to lock the hubs is max at 8

but the drop points to checking each side at the knuckle input

WRONG!!! Testing the output of the pvh solenoid valve and seeing a drop, means solenoid valve itself is bad. The hubs arent even in the vaccuum circuit at that time.