Re: [MBZ] '85 123 vacuum system

[fmiser via Mercedes]

> RA wrote:
> 
> I finally reached the point where the engine will not shut
> off when removing the key last week.  I must use the stop
> button under the hood each time.  The door locks also
> stopped working.

Classic symptoms of a failing vacuum control system.  It could
be lines or hoses - but I rarely see anything but the "vacuum
element" fail.  (I don't really like the word "vacuum
element", but that's the word Mercedes uses in the manual for
the vacuum actuators.)

> Dan wrote:
> This is all of maybe 10-15 minutes worth of diagnostics with a MityVac

> Rick wrote:
> 
> Buy a Mity Vac. Do it yourself.

> Rich wrote:
> 
> First is to put your mity-vac (HF sells a version for cheap
> but a "real" one is not that much anyway)

> Curt wrote:
>
> Buy a MityVac and do it yourself

I contend that a MityVac is unnecessary.  It is just a vacuum
source - but so is the pump on the front of the engine.

A vacuum gauge is handy, but even just a finger over the end
of a hose can be enough to the difference between strong
vacuum and weak-because-there-is-a-leak.

Unlike a MityVac, the engine vacuum is only available with the
engine running and it's harder to move from door to door.

To troubleshoot, first make sure the source vacuum is strong.
If the power brakes actually have power assist, then the
vacuum pump is probably okay.

Next check at the "T" near the booster.  By "check" I mean
"put a finger over the end and feel the pull".  Then start
"following" the vacuum forward 'till you figure out where it's
getting lost.  

Twigs or golf tees are pretty much required to plug various
lines to isolate.

With a MityVac you can check each branch - arguably the easier
way to do it, but I have identified and isolated many vacuum
problems while I was many miles away from my MityVac

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

Re: [MBZ] '85 123 vacuum system

[Jim Cathey via Mercedes]

he is not getting the 20 psi to restore all functionality.


Atmospheric pressure is less than 15psi.  Vacuum is customarily
measured in inches or mm of mercury, not (negative) PSI.

Your guy's being pretty sloppy with his terminology.  Perhaps that's
not all that is sloppy?

-- Jim


___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

Re: [MBZ] '85 123 vacuum system

[Rich Thomas via Mercedes]

Yeah what they said.  First is to put your mity-vac (HF sells a version 
for cheap but a "real" one is not that much anyway) on a hose near the 
brake booster where some branch off, and see if you are actually getting 
vacuum from the vac pump.  The diaphragms tear in them over time and 
vacuum gradually decreases.  Or it could be bad/cracked lines or tees up 
there under the hood, I ended up bodging some brass barbs and tees into 
the system by the brake booster because the plastic things were all 
brittle.  Lines crack and leak too.


From that set of branches you can start testing what is leaking if the 
pump is sucking right, could be the brake booster diaphragm or anything 
in the door lock system.  You can stick a pencil or a golf tee in those 
lines at the main tee there by the brake booster and see if that 
restores your brakes and shutoff, in which case you can leave the line 
going to the doors disconnected and at least have brakes and shutoff 
until you resolve the issue further downstream.


If you don't want to fool with it for now, get about 6 ft of vac line 
and run it to the shutoff then the other end into the cabin where you 
can get it, suck on it to shut off the car.  You still won't have brakes 
but that will alleviate the shutoff process.


I have a writeup with pics on changing the vac pump diaphragm, it is not 
particularly hard just a bit fiddly.


--R



On 9/1/15 12:20 PM, Rick Knoble via Mercedes wrote:

RA writes:


‎ I am losing confidence in his >ability to properly
troubleshoot and repair the >system.
Any thoughts on where else to >look?

Buy a Mity Vac. Do it yourself.

It isn't too terribly difficult to T/S vacuum problems, but it is time 
consuming, and much like electrical troubleshooting, you must possess the 
ability to think logically, and in a straight line.
Isolate one system at a time, vacuum it down, etc.

I have a comprehensive vacuum troubleshooting guide I received from Craig 
several years ago. I can post it online, with a link if you wish.
‎
Rick
Sent from my BlackBerry Z10

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com




___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

Re: [MBZ] '85 123 vacuum system

[Curt Raymond via Mercedes]

Hi there, do you have a first name?
Your first bet that he's incompetent is he says 20psi. PSI is a pressure 
measurement, vacuum is measured in inches of mercury.
The steps are dead simple, find the first T after the pump (on the front of the 
engine) and cap it. Pull a vacuum on the engine side and see if it holds, if 
not theres a problem in the pump or the line, fix that. If that holds move to 
the next junction. Cover everything under the hood first, then move to the 
driver's footwell and track throughout the car. 
Buy a MityVac and do it yourself, very rewarding.
-Curt
  From: RA via Mercedes <mercedes@okiebenz.com>
 To: Mercedes Discussion List <mercedes@okiebenz.com> 
Cc: r...@rhonald.me 
 Sent: Tuesday, September 1, 2015 12:01 PM
 Subject: [MBZ] '85 123 vacuum system
   
I finally reached the point where the engine will not shut off when
removing the key last week.  I must use the stop button under the hood
each time.  The door locks also stopped working.  A mechanic has found
one source in the drivers door and something else under the hood.  He
says there is a still a leak somewhere, he is not getting the 20 psi to
restore all functionality.  He says he is not getting any air to the
tailgate area.

I received an MBZ parts catalog and am reviewing the Vacuum System
1977-85 on page 15.  I am losing confidence in his ability to properly
troubleshoot and repair the system.  

Any thoughts on where else to look?

Thanks

R

1985 300TD 241,000 miles


 

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com



  
___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

Re: [MBZ] '85 123 vacuum system

[Rick Knoble via Mercedes]

RA writes:

>‎ I am losing confidence in his >ability to properly
>troubleshoot and repair the >system.  

>Any thoughts on where else to >look?

Buy a Mity Vac. Do it yourself.  

It isn't too terribly difficult to T/S vacuum problems, but it is time 
consuming, and much like electrical troubleshooting, you must possess the 
ability to think logically, and in a straight line. 
Isolate one system at a time, vacuum it down, etc.  

I have a comprehensive vacuum troubleshooting guide I received from Craig 
several years ago. I can post it online, with a link if you wish. 
‎
Rick 
Sent from my BlackBerry Z10

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

[MBZ] '85 123 vacuum system

[RA via Mercedes]

I finally reached the point where the engine will not shut off when
removing the key last week.  I must use the stop button under the hood
each time.  The door locks also stopped working.  A mechanic has found
one source in the drivers door and something else under the hood.  He
says there is a still a leak somewhere, he is not getting the 20 psi to
restore all functionality.  He says he is not getting any air to the
tailgate area.

I received an MBZ parts catalog and am reviewing the Vacuum System
1977-85 on page 15.  I am losing confidence in his ability to properly
troubleshoot and repair the system.  

Any thoughts on where else to look?

Thanks

R

1985 300TD 241,000 miles


 

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com

Re: [MBZ] '85 123 vacuum system

[Dan Penoff via Mercedes]

This is all of maybe 10-15 minutes worth of diagnostics with a MityVac.  It's 
vacuum, not pressure, so I'm confused why they would reference a positive 
pressure.

If you have access to a MityVac and some time, let me know and I can outline 
the steps. It's stupidly simple once you know how.

Dan

Sent from my iPad

> On Sep 1, 2015, at 12:01 PM, RA via Mercedes  wrote:
> 
> I finally reached the point where the engine will not shut off when
> removing the key last week.  I must use the stop button under the hood
> each time.  The door locks also stopped working.  A mechanic has found
> one source in the drivers door and something else under the hood.  He
> says there is a still a leak somewhere, he is not getting the 20 psi to
> restore all functionality.  He says he is not getting any air to the
> tailgate area.
> 
> I received an MBZ parts catalog and am reviewing the Vacuum System
> 1977-85 on page 15.  I am losing confidence in his ability to properly
> troubleshoot and repair the system.  
> 
> Any thoughts on where else to look?
> 
> Thanks
> 
> R
> 
> 1985 300TD 241,000 miles
> 
> 
> 
> 
> ___
> http://www.okiebenz.com
> 
> To search list archives http://www.okiebenz.com/archive/
> 
> To Unsubscribe or change delivery options go to:
> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
> 

___
http://www.okiebenz.com

To search list archives http://www.okiebenz.com/archive/

To Unsubscribe or change delivery options go to:
http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com