Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 05-28-2003, 06:21 PM
TNM
Guest
 
Posts: n/a
Post Vacuum locks - FAQ

I know this is probably a dumb and too often asked question. But is there a FAQ for testing Vacuum locks? I can sometimes hear a hum comming from the spare tire when I shut the car down - so I don't think the pump isn't working but, none of the locks work and they never have for the year I've owned this car and I'd liek to tinker with it as I'm going to re-do my leather and fix some things I've been ignoring.
Thanks,
Tom Martin

Reply With Quote
  #2  
Old 05-28-2003, 07:27 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
Would help to know what car. Sounds like a W126 if you hear a pump in the spare tire well.

Things you can do to isolate the problem:

- pull a vacuum on the line to the pump. The doors should lock.

- test the vacuum from the pump right when you lock the driver's door by key. I don't know the spec but I expect it should be something like 15inHg for 3-4 seconds.

That tests the locking function. Unlocking uses pressure so you can run similar tests using pressure equipment. I don't know what the pressure spec is for the pump or the limits of the door lock actuators. Not an issue with vacuum since a MightyVac isn't powerful enough to make an actuator implode or rupture a sound diaphragm.

Sixto
91 300SE
87 300SDL
83 300SD
Reply With Quote
  #3  
Old 05-28-2003, 09:48 PM
TNM
Guest
 
Posts: n/a
sorry, I thought that was somehow posted - it is an 83' 300SD
Tom
Reply With Quote
  #4  
Old 05-29-2003, 07:19 PM
Registered User
 
Join Date: Sep 2000
Location: Shalimar, FL
Posts: 79
Tom, If you have a mightyVac its easy and quick to trace the problems. start at the pump, unhook the vacuum line and hookup the mightyvac, have someone lock and unlock the drivers door and watch the gauge to make sure you have vacuum or pressure. If the pump is working replace the vacuum line, you will see a "Y" that branches to the filler door, pull that line and plug it with a golf tee. actuate the pump and check the door locks, if they start working your problem is probably a leaking filler door actuator. Next swap the golf tee into the other side of the "Y" and check the filler door. If the filler door is good reconnect and proceed to the passenger compartment. On the passengers side under the carpet you will find a plastic chase that contains the vacuum lines and other wiring. This vacuum line splits into 3, going to both passenger side doors and the drivers side passenger door. Reomove the lines one at a time and plug with the tee, you will probably find that when you plug one, hopefully just one, of the lines everything else will start working, then just replace the actuators that are bad. If you check Thomaspin's site it has some good instructions on removing the door panels, the actuators are easy replaced once the panels are off. Hope this helps.

Bob H.
Reply With Quote
  #5  
Old 05-30-2003, 12:02 AM
TNM
Guest
 
Posts: n/a
Thanks,
I don't have a Mightyvac or know what one is - I searched ebay but, came up with no results. How much are they and where can I get one?
Thanks.,
Tom
Reply With Quote
  #6  
Old 05-30-2003, 03:43 AM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
Sears has them for $50-70. Sears is not the cheapest place to find one. They come in plastic or metal, with a thousand attachments or none, with gauge and without gauge... you get the picture.

Try an eBay search on Mityvac or Mity Vac. I got a few hits.

Sixto
91 300SE
87 300SDL
83 300SD
Reply With Quote
  #7  
Old 05-30-2003, 06:20 PM
MBwerker
Guest
 
Posts: n/a
Mity-Vac

Some Wal-Mart's now carry them for about $24. Look at Walmart.com. If you can, try to find the model that comes with the plastic tank it's handy for pulling fluid out of master cylinders before brake jobs, emptying hydraulic tanks and power steering tanks without making a mess.
Reply With Quote
  #8  
Old 03-18-2004, 10:27 PM
Registered User
 
Join Date: Mar 2004
Location: SF Bay area
Posts: 2
Just how much work to fix the locks?

And is it worth it?

Enough reading through here shows me my problem with the door locks must be a vacuum problem. I keep shilling out dollars to fix necessary fixes for this old car. Things like cruise control and car antenna don't get fixed. What's a 1985 300SD with 250,000 miles worth--$2000? Is it worth it to continually fix things like this? I consider working locks an important security issue.

Thanks.
Reply With Quote
  #9  
Old 03-18-2004, 10:59 PM
Registered User
 
Join Date: Jan 2002
Posts: 18,350
Your locks should work manually without vacuum so they shouldn't be a security issue.
It usually doesn't take much money to fix vacuum problems, just time troubleshooting.
__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
Reply With Quote
  #10  
Old 03-19-2004, 12:52 AM
Registered User
 
Join Date: Feb 2004
Location: Wisconsin
Posts: 41
vacumn door locks

I had a similar problem on my '82 240D 8 years ago, plus the engine would not turn off. I removed all the door panels and tested each door diaphragm lock with a vacum tester I bought at an auto parts store. Three of the them were leaking and I replaced them with parts from Performance Products. All doors, trunk, and gas flap have locked fine since, and engine turns off. This is not an expensive repair, just requires diligence and some spare time.
__________________
DHB
Reply With Quote
  #11  
Old 03-19-2004, 03:15 PM
Registered User
 
Join Date: Mar 2004
Location: SF Bay area
Posts: 2
Thank you all.

Looks like I'll have to do some more work. Hopefully husband will help me. The doors seem to me to be quite heavy.

By the way, when the car locks are not working one cannot even push down the lock button, with the car doors open or closed. The buttons seem to be frozen upright. That concerns me because I work until quite late and go to my car in a remote parking lot. I haven't been able to lock the doors from the inside.

Lately I have found I can use the key to lock the front door from the outside. Then, if I wait 15 minutes or so, I have been able to push down the lock button on the back door, driver's side.

We'll see what we can do.

THANKS!
Reply With Quote
  #12  
Old 03-19-2004, 03:46 PM
Rick Miley's Avatar
Spark Free
 
Join Date: Jun 1999
Location: Land O Lakes, FL
Posts: 3,086
On Mercedes-Benz cars there is a feature that will not allow you to push the lock knob down while a door is open. This is to keep you from locking the keys in the car. With the door closed, you should be able to lock or unlock from the knob, as well as lock or unlock with the key from outside. I wrote a lengthy description of how the vacuum locks work on a 240D, but that is not applicable to your model. The W126 (your car) with electric pump has a single "air" line to each door that uses either pressure or vacuum to lock and unlock. (I forget which does which). If you get a MityVac and start testing from the pump location in the trunk, it should not be too hard to trace. But if you'd rather do without the power locks altogether, you could just pull all the lines off at the pump.

As for continually fixing stuff, these cars retain their value a lot better if you do. Most things are not very difficult to repair, although you do have to learn the "Mercedes way." And generally, repairs last a very long time so you should not end up doing the same thing over and over.
__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References
Reply With Quote
  #13  
Old 03-20-2004, 05:08 AM
Registered User
 
Join Date: Dec 2002
Location: New Jersey
Posts: 218
I have the same car (1938 300SD) and my locks just went out. I am also going to have to find the problem. My locks all work manually except I had to pull the fuel release from inside the trunk to get it open. Also my trunk will only open with the key. It remains locked. Any suggestions or do I have to test everything?

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 10:49 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page