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Discussion Starter #1
I noticed my 4wd would not auto lock the other day when I needed but the hubs manually locked in 4wd. So I searched on here and found out it is a vacuum leak. I tried the vents to defrost switch when in 4wd but didnt notice any change. The vacuum did run constant while it was in 4wd though. Does this mean it is a line between the valve and hubs? I inspected the hoses from the hub to where they connect on the bracket on the frame but didnt notice any cracks or anything.
 

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Discussion Starter #2
Replaced the hoses from the hub to connector, didnt fix it. Not sure where to go next.
 

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That might have fixed it after I tried it again. Does the vacuum pump still run for like 30 seconds after it switches to 4wd? It eventually cut off, but i havent got a chance to try it in 4wd yet.
 

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it's a 45 second pulse to lock the hubs and less to unlock

so a leak will only change the defrost for so long
 

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Discussion Starter #5
Tried it in 4wd. Doesn't work. Not sure what to do. Checked under dash and all the connections around vacuum.
 

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Tried it in 4wd. Doesn't work. Not sure what to do. Checked under dash and all the connections around vacuum.
99 percent of the time, ESOF problems are caused by vacuum leak.

First place to look is in the passenger footwell. Look for a disconnected vacuum line where someone kicked it apart.

If that's not the problem, then look around each front hub for a disconnected vacuum line. Trace the vacuum line back towards the cab, looking for a disconnected or loose connection.

If you don't fine any obvious disconnects, then your easy diag is over. Here's the next step:

SECTION 308-07A: Four-Wheel Drive Systems 2002 F-Super Duty/Excursion Workshop Manual

GENERAL PROCEDURES

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Hublock Vacuum System Leak Test

NOTE: This procedure requires the use of a calibrated vacuum gauge that is accurate to within a minimum of 0.1 in-Hg. It is recommended the Pressure Vacuum Module 105-R0099 or equivalent be used.

Make sure hublocks are in the AUTO position.

Lift and support the vehicle off the ground until the front tires can be spun freely. Refer to Section 100-02 .

NOTE: The engine is required to be at idle during the following steps to supply the vacuum required for the hublocks to engage and disengage.

Start the engine and allow to idle.

Turn the mode select switch (MSS) to the 2WD position and wait 15 seconds. If switching from 4X4 mode, wait an additional 45 seconds.

Disconnect the vacuum line at the right front knuckle and install a vacuum gauge on the line.

Disconnect the vacuum line at the left front knuckle and plug the line.

NOTE: Normal operation applies engagement vacuum for 45 seconds and then drops to 0 in-Hg.

Turn the MSS to 4X4 and observe the vacuum reading. The vacuum reading should remain at or above 10 in-Hg for 45 seconds.

NOTE: Normal operation applies regulated disengagement vacuum for 15 seconds and then drops to 0 in-Hg.

Turn the MSS to 2WD and observe the vacuum reading. The vacuum reading should remain between 5.8 and 7.3 in-Hg for 15 seconds.

Remove the vacuum gauge and connect the vacuum line at the right front knuckle.
Turn the MSS to 4X4.

NOTE: The right front axle shaft and universal joint should turn.

Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint.

Turn the MSS to 2WD.

NOTE: The right front axle shaft and universal joint should not turn.

Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint.

Install the vacuum pump and gauge line on the knuckle and pump to 20 in-Hg.

If vacuum drop is less than 0.5 in-Hg in 30 seconds install a new hublock with a new O-ring seal kit. Refer to Hublock in this section.

If vacuum drop is greater than 0.5 in-Hg in 30 seconds install a new hublock. Refer to Hublock in this section.

Repeat steps 1 through 13 for the LH hublock. If results are not as indicated, Go To Pinpoint Test G for further diagnosis of the hublock system.

Griz
 

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Discussion Starter #8
99 percent of the time, ESOF problems are caused by vacuum leak.

First place to look is in the passenger footwell. Look for a disconnected vacuum line where someone kicked it apart.

If that's not the problem, then look around each front hub for a disconnected vacuum line. Trace the vacuum line back towards the cab, looking for a disconnected or loose connection.

If you don't fine any obvious disconnects, then your easy diag is over. Here's the next step:


Griz
Well, I guess my easy is over. I checked, rechecked, and rechecked connections.

The only thing I noticed was this piece on the vaccum pump. You can see my finger pointing to it. Is this supposed to be open?

 

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Discussion Starter #9
Also, if there was an obvious leak, wouldnt I feel the air leaking around the leak when the pump is running? I hate to take it to get fixed, but I do know the people at the local dealership and they are good. I think this is what my next action is.
 

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Well, I guess my easy is over. I checked, rechecked, and rechecked connections.

The only thing I noticed was this piece on the vaccum pump. You can see my finger pointing to it. Is this supposed to be open?
Mine doesn't have a hose at that connection either. If you can get yourself a vacuum Gage or borrow one, it isn't that hard to check the 4x4 vacuum system out. Pull both vacuum lines off the hubs. Plug one and attach the vacuum Gage to the other hose/line. If you have 10 or more in-Hg when you select 4x4 than the hubs should be engaging. If you don't have 10 in-Hg then move the vacuum Gage back towards the PVH (Pulse Vacuum Hublock solenoid) and connect the Gage there. If you still don't have 10 or more in-Hg then move the Gage to the Vacuum reservoir and monitor it's output vacuum. Fix whatever you find wrong. If your engage vacuum reading was correct when the lines to the hubs were disconnected. Then plug one line back into its hub and monitor the other line with your vacuum Gage. Repeat the setup with the other hub connected and monitor the vacuum reading. If one hub reading was bad...then you most likely have a vacuum leak in that hub or hublock that needs to be fixed. Sometimes one of your vacuum lines will look good but isn't and the easiest way to tell is by monitoring the vacuum system with a vacuum Gage. Are you able to get into 4x4 by manually locking your hubs?

Griz
 

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Discussion Starter #11
Yes, I can manually lock it into 4wd. Thats how I found out it didnt work. Stuck in a field with a trailer and finally manually locked in 4wd to get out. Any specific vacuum gauge to use? Do auto stores lend those out?
 

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Yes, I can manually lock it into 4wd. Thats how I found out it didnt work. Stuck in a field with a trailer and finally manually locked in 4wd to get out. Any specific vacuum gauge to use? Do auto stores lend those out?
Than you are only dealing for a vacuum problem since you can lock the hubs and be in 4x4.
As long as the vacuum Gage is accurate it doesn't matter. Not sure about auto parts store lending out a vacuum Gage but I would check them first before buying one. Sometimes they ask for a deposit that you get back when you return the tool/Gage. There are 0-rings in the hubs that can cause a leak...but you really need to isolate the problem before tearing into the hubs. Here is a link to a web site on how to lube the hublocks. Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page And another link on how to lube the hub needle bearing. Welcome to guzzle's 4x4 Needle Bearing Maintenance Web Page In these links they talk about vacuum leaks that can be caused by the hub's o-ring seals.

Griz
 

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Discussion Starter #13
Thanks
 

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Discussion Starter #15
I will, I am sending it to a local shop for another issue and was going to get them to check out the leak problem also. I couldn't come up with a vacuum tester and I need my other issue fixed asap.
 

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Discussion Starter #17
They are saying the vacuum leak is the solenoid that controls it. Also had a leak I had been noticing, it was the fuel filter o ring, they will be replacing fuel filter. The reason I couldn't get it to start was the cam sensor went out that they are replacing under recall. They are also going to try and adjust the overhead to the correct reading with the bigger tires. They said all that should be under $200 w/ labor. Didn't think it was that bad considering I am new to diesels and couldn't figure out what was wrong.
 

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They are saying the vacuum leak is the solenoid that controls it. Also had a leak I had been noticing, it was the fuel filter o ring, they will be replacing fuel filter. The reason I couldn't get it to start was the cam sensor went out that they are replacing under recall. They are also going to try and adjust the overhead to the correct reading with the bigger tires. They said all that should be under $200 w/ labor. Didn't think it was that bad considering I am new to diesels and couldn't figure out what was wrong.
That's not bad considering the parts alone are over $100. Glad to hear you have all your problems fixed.

Griz
 

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your 4wd is not part of your a/c or heater control. it is a stand alone system. there is a seal on your axle shaft ends. these seals go bad . look at the axle joint . grab it can u move it up and down. if so it is probably bad. best way to check is with a vacuum pump. if it wont hold vacuum the seal is bad
 

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your 4wd is not part of your a/c or heater control. it is a stand alone system. there is a seal on your axle shaft ends. these seals go bad . look at the axle joint . grab it can u move it up and down. if so it is probably bad. best way to check is with a vacuum pump. if it wont hold vacuum the seal is bad
Actually the vacuum to operate the Auto-lock hubs Tees off the same vacuum reservoir as the HVAC controls.

Griz
 
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