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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| '02 G500 Differential Lock System
I have searched, but found little detail regarding the front and rear differential lock actuator system. I have found some very clear drawings and explanations of the system in Harald's "Work Shop" CDs so I have a pretty academic understanding of how things are suppose to work. I've also spend a few hours under the truck having a look at things. So here is the problem: No hydraulic fluid is getting to the front locker. There is fluid in the reservoir and the center and rear lockers seem to be working just fine. As part of the major service I just had my mechanic do a flush on the system. When I received the truck back I found the reservoir empty. He says he bleed the whole system, but forgot to refill the reservoir. After refilling and bleeding the rear is fine, but as I said there is no fluid getting to the front locker actuator. I verified this by removing the end assembly in which the inlet line and bleeder screw are mounted. See below ...
I gather that I should be looking for a clog between the inlet of the front intensifier and the front actuator ... 
Any thoughts on this would be much appreciated.
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DUTCH
Administrator Doppelgänger
Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
| RE: '02 G500 Differential Lock System
Indiana Drew - 6/22/2010 6:38 PM
I gather that I should be looking for a clog between the inlet of the front intensifier and the front actuator ...
Or you have a dead intensifier
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: '02 G500 Differential Lock System
What kind of bleeding was done? I've always used a pressure bleeder for this purpose. That pushes fluid into the reservoir under continuous pressure and out the bleeders when they are opened. If you don't get fluid with a pressure bleeder then I'd suspect a crushed or clogged pipe.
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: '02 G500 Differential Lock System
DUTCH - 6/22/2010 6:04 PM Indiana Drew - 6/22/2010 6:38 PM
I gather that I should be looking for a clog between the inlet of the front intensifier and the front actuator ...
Or you have a dead intensifier
I'd include the intensifier for sure - I don't think it could be anything between the reservoir and where the fluid line splits ... Is the intensifier a rebuild-able item? AlanMcR - 6/22/2010 6:33 PM What kind of bleeding was done? I've always used a pressure bleeder for this purpose. That pushes fluid into the reservoir under continuous pressure and out the bleeders when they are opened. If you don't get fluid with a pressure bleeder then I'd suspect a crushed or clogged pipe.
The mechanic used a power bleeder (pressure tank) - He also replaced the rear two TC bushings, engine mounts, and suspension bushings. He also had the spring shims done by another shop. I don't know if he had that done before of after the bleed ... I wonder if it is possible to crush a line along the driver's side front quarter doing any of those jobs? I suppose checking the outlet side of the intensifier would be the next logical point ...
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Fernando BR
Date registered: Jan 2007
Location: Brasil
Vehicle(s): G500/05 300GE/91 300GD/80
| Re: '02 G500 Differential Lock System
Bad intensifier piston always down blocking fluid ? Good it didnt stuck with front locker on.
Edited by Fernando BR 6/23/2010 1:03 AM
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: '02 G500 Differential Lock System
For how long should the vacuum pump run with locker/s engaged? |
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DUTCH
Administrator Doppelgänger
Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
| RE: '02 G500 Differential Lock System
Indiana Drew - 10/31/2010 5:20 PM
For how long should the vacuum pump run with locker/s engaged?
It depends on who you talk to.
When my vacuum pump was brand new, it would shut off when it reached a certain vacuum. I haven't checked lately, but it seems to run longer - perhaps continuously now. See attached.
Attachments
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 DiffLockVacuumPump.pdf (113KB - 72 downloads)
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: '02 G500 Differential Lock System
The attached makes sense - I'll have to find a place to give the lockers a longer test, but the front locker disengaging while driving on the beach was what got me looking at the system in the first place ... Looks like it might be time to look for a vacuum leak or to the age of the vacuum pump. I guess as long as the pump running while the lockers are in use is not going to hurt anything, I really won't worry. It also seems the pump cycles on and off with just the cent dif engaged but runs with the rear and front locked ... Thanks Dutch ... |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: '02 G500 Differential Lock System
Indiana Drew - 10/31/2010 2:20 PM
For how long should the vacuum pump run with locker/s engaged?
With the engine running, the pump should run all the time with lockers engaged.
With the engine off, and lockers engaged, the pump should run for about 30 seconds or so, and then shut itself off when the pressure gets low enough.
This is a good test of your vacuum integrity - if the pump never shuts off when the engine is off, then you have a leak. |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: '02 G500 Differential Lock System
W5YK - 10/31/2010 11:53 PM Indiana Drew - 10/31/2010 2:20 PM For how long should the vacuum pump run with locker/s engaged? With the engine running, the pump should run all the time with lockers engaged. With the engine off, and lockers engaged, the pump should run for about 30 seconds or so, and then shut itself off when the pressure gets low enough. This is a good test of your vacuum integrity - if the pump never shuts off when the engine is off, then you have a leak. Good point - thanks RR! |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: '02 G500 Differential Lock System
W5YK - 10/31/2010 11:53 PM Indiana Drew - 10/31/2010 2:20 PM For how long should the vacuum pump run with locker/s engaged? With the engine running, the pump should run all the time with lockers engaged. With the engine off, and lockers engaged, the pump should run for about 30 seconds or so, and then shut itself off when the pressure gets low enough. This is a good test of your vacuum integrity - if the pump never shuts off when the engine is off, then you have a leak.
OK - RR's suggestion of engaging the lockers and switching off the engine to see how long the vacuum pump would run. Almost to the second it ran until 30 then switched off. Vacuum system has integrity. Now I need to find a place where I can drive with the Lockers engaged to see if they still disengaging from time to time. I guess I can put it on jack stands, too ... |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| Reviving '02 G500 Differential Lock System
As Dutch had suggested just after my original post, I have nothing left to check or blame with my front and rear lockers engaging and then disengaging a brief time later according to the indicator lights. Any ideas as to general cost of replacement intensifiers or the difficulty level of replacing them? |
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: Reviving '02 G500 Differential Lock System
Not to incite panic, but this was exactly the behavior observed before one of our diffs destroyed a bearing on the Baja trip. You might want to drain the rear diff and see what comes out.
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: Reviving '02 G500 Differential Lock System
AlanMcR - 4/7/2011 11:55 AM Not to incite panic, but this was exactly the behavior observed before one of our diffs destroyed a bearing on the Baja trip. You might want to drain the rear diff and see what comes out.
I'll give it a look, but I had the fluid changed 8 or 10 months ago and was not told anything was chunky in it. Might as well change it - hope I have some Redline on the shelf ...
There was however defiantly lots of build up at the banjo fitting going into the actuator of both front and rear that I attributed to lack of use in 9 years. I don't know how the intensifiers are built, but I had supposed that the gunk might have come from the breakdown of some rubber parts within. |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Reviving '02 G500 Differential Lock System
Indiana Drew - 4/7/2011 8:26 AM
As Dutch had suggested just after my original post, I have nothing left to check or blame with my front and rear lockers engaging and then disengaging a brief time later according to the indicator lights. Any ideas as to general cost of replacement intensifiers or the difficulty level of replacing them?
Drew,
we have figured the following situation........somehow the the finger of the diff locker actuator got bend just slightly.
The "offset" was large enough for the locker not able to engage now all the way into the lock gear of the diff carrier.
The results might have been mushrooming the tip of the gears do to higher stress at a smaller area.
Small pieces might have been dislodged from the gear tip and gotten into the gear oil.
Next to the locker gear sits the large left diff carrier bearing and the small hardened gear pieces might have damaged that HD bearing to an extend, that the whole bearing guts was dumped into the diff /axle housing.
Eventual one of the bearing rollers got caught between the pinion and the ring gear - not a pleasant feeling and sound at all
So, IMHO it is important to adjust the diff locker actuators on both axle in order to offset a slightly bend finger which could lead to a real expensive repair.
In order to adjust the actuator, the unit needs to be charged (turn on the locker switch), have both wheels off the ground, unbolt then the actuator and move it toward the diff housing while turning the wheels so the locker can engage. Move the actuator all the way until the lock is fully engage......re-tighten the four mounting bolts.
In my case, with the damaged rear axle - no prior noises to hear - just a day earlier the rear locker would not engage any more like before and got kicked out real hard a couple of times.
The picture shows the real damaged/bend finger
 (IMG_5722 (Medium).jpg)
Attachments
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IMG_5722 (Medium).jpg (84KB - 3 downloads)
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: Reviving '02 G500 Differential Lock System
Karl
I don't recall if we removed the entire actuator last year when we changed the fluid and remover the gunk from the banjo fittings ... It is an easy thing to do especially if it is up on a lift ... I'll check that.
Thanks |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: Reviving '02 G500 Differential Lock System
Is there any sort of diagnostic test to do with the intensifiers? I know there is nothing in the STAR as the units are completely analog ... My indi shop guy says the dealer wants a pretty penny for them so I hope I find something through our tried and true sources assuming they turn out to be the issue ... |
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koly
Elite Veteran
Date registered: Jul 2006
Location: Scottsdale, AZ USA
Vehicle(s): 2000 G500
Posts: 823
| RE: Reviving '02 G500 Differential Lock System
You may also want to check the solenoid/switches on the firewall - they run about $70 ea I recently had two of the three go bad almost simultaneously.
They were both showing good readings on a voltmeter but for some reason they weren't completing the circuit properly when engaged.
Probably not what's causing your troubles, but maybe worth a look before other more costly measures... |
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DUTCH
Administrator Doppelgänger
Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
| RE: Reviving '02 G500 Differential Lock System
Indiana Drew - 4/7/2011 10:46 PM
Is there any sort of diagnostic test to do with the intensifiers? I know there is nothing in the STAR as the units are completely analog ... My indi shop guy says the dealer wants a pretty penny for them so I hope I find something through our tried and true sources assuming they turn out to be the issue ...
MBUSA MSRP = $340 ea. Can be had for around $265 from the right dealer. |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: Reviving '02 G500 Differential Lock System
Thanks Dutch!
I have been told it is probably not the in intensifiers if fluid is flowing freely though the system and none is being lost ... Any other points of diagnosis? |
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