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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: G55 Diff Lock Vacuum Pump
fernweh - 9/25/2011 12:29 PM
Front and rear lockers normaly will work in the case that vacuum pump is out of combat cause engines produces enough vacuum. Diff locker that is only pneumatic wont work without vacuum pump.
The TC diff lock in my G-500 was working, but slower with the defective vacuum pump. Please remember, that the defective pump had also quit a vacuum leak besides the motor being burned up. When I removed the pump out of the system and temporary connected its vacuum lines together, the locker engagement time improved.
Karl,
Your observation agrees with the literature published by MB. If the vacuum pump is weak or missing, the front locker may have trouble functioning correctly. See attached.
 (DiffLocks2.jpg)
Attachments
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 DiffLocks2.jpg (156KB - 1 downloads)
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Fernando BR
Date registered: Jan 2007
Location: Brasil
Vehicle(s): G500/05 300GE/91 300GD/80
| RE: G55 Diff Lock Vacuum Pump
fernweh - 9/25/2011 12:29 PM
BTW early 463 small pump is enough to the job , why use that monster they introduced on G500? My 300GE never had lockers troubles after 20 years ( my 500 also but has only 6 years) . G 500 2001 + system is much more complicated
This Locker system is identical to the earlier W463's, just a vacuum pump has been added - the old separate switches are complicated - the "new" swichpacks are digital nature and follow the technologies applied to newer vehicles.
Karl , a big vacuum pump . Early 463 system has a vacuum pump too , but smaller .You know that - I forgot your old truck was a 300GE.
Hi-tech.....I have doubts about 463 reliability , not in the desert or at the beach , but into real mud situations . Dont really know what is going to happen with wheels speed sensors for example after miles of water/mud contact and resistance ( I always used 300GE with no ESP or 300GD for that) .....But of course its a personal point of view and i respect your.
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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: G55 Diff Lock Vacuum Pump
Fernando BR - 9/25/2011 10:25 AM
fernweh - 9/25/2011 12:29 PM
BTW early 463 small pump is enough to the job , why use that monster they introduced on G500? My 300GE never had lockers troubles after 20 years ( my 500 also but has only 6 years) . G 500 2001 + system is much more complicated
This Locker system is identical to the earlier W463's, just a vacuum pump has been added - the old separate switches are complicated - the "new" swichpacks are digital nature and follow the technologies applied to newer vehicles.
Karl , a big vacuum pump . Early 463 system has a vacuum pump too , but smaller .You know that - I forgot your old truck was a 300GE.
Hi-tech.....I have doubts about 463 reliability , not in the desert or at the beach , but into real mud situations . Dont really know what is going to happen with wheels speed sensors for example after miles of water/mud contact and resistance ( I always used 300GE with no ESP or 300GD for that ) .....But of course its a personal point of view and i respect your.
Thanks Fernando,
does your 300GE has ABS brakes?
If yes, you do have also wheel speed sensors and they do hold up in mud and water for many miles. Correct? Not much different than the G-500
Karl |
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: G55 Diff Lock Vacuum Pump
The wheel speed sensors in the front are inside the axle balls. No risk there. The rears are plugged into the drum brakes. Since the sensor itself is embedded in plastic, I doubt that it is much affected by mud. I think they are most often damaged by maintenance. For example trying to pull them out for a front axle rebuild.
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G55 Diff Lock Vacuum Pump
HELH81953021 arrived!
Looks identical to the original Hella pump. Only the electrical connectors are 2 instead of 3. Its missing any Hella labeling (could it be a China knockoff?)
But anyway, it works just fine for $76!
 (compare.jpg)
 (hella.jpg)
 (no-name.jpg)
 (new-pump.jpg)
 (motor.jpg)
Attachments
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compare.jpg (342KB - 0 downloads)
hella.jpg (166KB - 1 downloads)
no-name.jpg (170KB - 0 downloads)
new-pump.jpg (189KB - 0 downloads)
motor.jpg (154KB - 2 downloads)
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| Re: G55 Diff Lock Vacuum Pump
the last image shows the melt down inside the pump
more detailed images here:
http://carlosnpainter.smugmug.com/Cars/G500-vacuum-pump/19303746_Hc...
Edited by 4x4abc 10/2/2011 1:35 AM
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/2/2011 1:00 AM
HELH81953021 arrived!
Looks identical to the original Hella pump. Only the electrical connectors are 2 instead of 3. Its missing any Hella labeling (could it be a China knockoff?)
But anyway, it works just fine for $76!
When you opened the old one, were you able to see what the 3rd connector was for?
MB has also changed the mounting orientation on the 2002+ trucks to make it easier to uninstall and install. On my G500, the right angle bracket is not present; and the pump is mounted directly flat to the inner fenderwall, which makes those mounting nuts much harder to access. |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G55 Diff Lock Vacuum Pump
Dutch,
you see the 3rd connector in the last image (motor.jpg) - it is used to join one of the leads from the motor with the pressure switch
ground goes from left pin to the pressure switch - from pressure switch to center pin - from center pin to motor
plus goes from right pin to motor |
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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: G55 Diff Lock Vacuum Pump
Sehr gut Harald!
That shows us the interconnection with the pressure switch.
If the vacuum system does not have any leaks, the vacuum pumps runs only until the switch off point (vacuum) is reach - regardless if motor is running or just ignition on, but depended on the center lock switch.
Richard,
now the big question:
on the switch pack modification, will only the center lock or also the other two locker switches trigger the +12VDc to the pump?
Karl |
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/2/2011 8:29 AM
Dutch,
you see the 3rd connector in the last image (motor.jpg) - it is used to join one of the leads from the motor with the pressure switch
ground goes from left pin to the pressure switch - from pressure switch to center pin - from center pin to motor
plus goes from right pin to motor
Using the center pin at the OEM pump would activate the pump without being turned off by the pressure switch.
So, it could be used to check if the pressure switch is inop
Karl |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G55 Diff Lock Vacuum Pump
Karl,
easy answer - the pump is only activated when you press the center diff lock switch.
The new pump turns off after a few moments when the intended vacuum is reached.
However, in my case the pump turns on briefly every 2 minutes or so - meaning, I have a vacuum leak somewhere. I hope, its not the diaphragm.
On a side note - the lower vacuum outlet (the one that connects to the pressure switch) had a fracture at the T. Don't know whether it was damaged during shipping/handling or whether it is indeed a cheap Chinese copy.
Since I do not have time to send the unit back, I fixed it with some creative vacuum line rigging. |
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/2/2011 6:34 PM
Karl,
easy answer - the pump is only activated when you press the center diff lock switch.
OK, our modified switch packs are lacking the ability to turn on the vacuum pump, when only the front or rear locker are chosen.
With an unmodified switch pack the pump is activated with the center diff lock switch, which has to be ON in order to lock the rear and front axle. The aux vacuum pump is being used to assist the engine's vacuum - create/maintain a better vacuum - for all locker operations.
Karl
Edited by fernweh 10/3/2011 11:16 AM
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G55 Diff Lock Vacuum Pump
Karl,
the engine vacuum is sufficient for front and rear lockers - but not for the transfer case, due to the lage diaphragm |
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/3/2011 2:59 PM
Karl,
the engine vacuum is sufficient for front and rear lockers - but not for the transfer case, due to the lage diaphragm
That certainly differs from the published MB documentation.
 (DiffLocks2.jpg)
Attachments
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DiffLocks2.jpg (156KB - 0 downloads)
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/3/2011 11:59 AM
Karl,
the engine vacuum is sufficient for front and rear lockers - but not for the transfer case, due to the lage diaphragm
Harald,
With an unmodified switch pack, the vacuum pump is always activated when any locker is engaged.
Mercedes probably would like to see a more or less constant vacuum for the locker engagements. Remember when switching off the locker that vacuum line is vented at the solenoid valve and for a new "deployment" of the locker the intensifier or diaphragm works best with a good strong vacuum.
Karl
Edited by fernweh 10/3/2011 4:35 PM
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G55 Diff Lock Vacuum Pump
well, most likely when a need for either front or rear locker arises, you have already your center diff lock activated (aux pump running).
I can only think of very rare circumstances where I would exclusively select one of the axle diff locks - most likely the front (extremely tight turn, where center and rear diff lock would hinder the tight turn). |
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MiN
Extreme Veteran
Date registered: May 2006
Location: Alpujarras, Spain
Vehicle(s): No cars, at all.
Posts: 555
| Re: G55 Diff Lock Vacuum Pump
The reason why I found that my vacuum pump wasn't working was because the rear diff lock kept dropping out. This would seem to indicate that I do need the vacuum pump to hold the diff lock in, which is what happend once the pump had been replaced. |
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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: G55 Diff Lock Vacuum Pump
4x4abc - 10/3/2011 7:06 PM
well, most likely when a need for either front or rear locker arises, you have already your center diff lock activated (aux pump running).
I can only think of very rare circumstances where I would exclusively select one of the axle diff locks - most likely the front (extremely tight turn, where center and rear diff lock would hinder the tight turn).
Mein reden seit '33......
I just got a new Vacuum gauge now, we can test the vacuum created by the running engine and together with the aux vacuum pump.
Any vacuum leak would be also detected.
Harald, get here early enough and we can play with the toys
Good night...
Karl |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: G55 Diff Lock Vacuum Pump
fernweh - 10/2/2011 3:50 PM
on the switch pack modification, will only the center lock or also the other two locker switches trigger the +12VDc to the pump?
Karl
Karl,
The vacuum pump is just wired in parallel with the center locker solenoid. The switch pack does not have any separate logic for it.
So if you have a modified switch pack and just a front or rear locker selected, the pump does not run.
On my G, this is not a problem The front and rear never drop out, even with a bit of throttle.
You could make it come on if you connected the pump via three diodes, one to each locker solenoid. But I did not see the need for that yet. |
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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: G55 Diff Lock Vacuum Pump
W5YK - 10/4/2011 7:33 AM
fernweh - 10/2/2011 3:50 PM
on the switch pack modification, will only the center lock or also the other two locker switches trigger the +12VDc to the pump?
Karl
Karl,
The vacuum pump is just wired in parallel with the center locker solenoid. The switch pack does not have any separate logic for it.
So if you have a modified switch pack and just a front or rear locker selected, the pump does not run.
On my G, this is not a problem The front and rear never drop out, even with a bit of throttle.
You could make it come on if you connected the pump via three diodes, one to each locker solenoid. But I did not see the need for that yet.
Thank you Richard,
I might want to install those interfaces in the future. I'm still baffled by the fact, that I lost the left main bearing of the differential carrier in my rear axle, the one next to the locker gears. I wasn't aware of any locker/vacuum problems at that time, but I do believe that small shavings from the locker gear started the whole mess.
Karl |
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