Add On Electric Vacuum Pump for W123 Locking System - PeachParts Mercedes-Benz Forum

Diesel911 · #1 06-23-2012, 02:08 PM

The reason for adding the Electric Vacuum Pump to my Locking system is that the Locking System has Vacuum Leaks and I disconnected it from the normal Vacuum source.
Before disconnecting the Vacuum I installed a crude Trunk Cable Puller to open the Trunk.

Using the Locks manually and using the Pull Cable to open the Trunk all seems OK except that my Wife often leaves the Car and Trunk or both unlocked. I just cannot rely on Her to lock the Car all of the time.

The Vacuum Pump was bought on eBay for previous project and is for a Saab or Volvo; used are in the $55-$75 range.

The Vac Pump does not ground though the Pump Body so wiring is straight forward; one wire is Positive to go to the Battery and the other is the Ground.
I did not mount the Pump on any Bracket if kind of fits into a pocket under the Fuse Box with the Fender Well in front of it.

I ran the Ground Wire through the Fire Wall Grommet where other wires are.

Removed the Hood Pull Lever and then the Plastic side molding on the lower driver’s side. That Molding attaches to part of the Plastic Floor Molding and I had to pull up the Floor mats and remove one Screw that holds the Molding to the floor.

I removed the Plastic Molding because at that point I did not know where I was going to drill the Hole for the Door Switch I was going to add.
After finding a suitable spot on the front Door Frame for the Door Switch I drilled and taped the Hole.

I ran the Ground Wire to the Switch that has little ears you can crimp over to attach the wire and screwed the Switch into the Door Frame. You need to screw the Switch all the way in and then back it out a little at a time until it is adjusted properly so it shuts off when the Door is closed but does not damage anything.

So I tested it out and it works. But, then I realized that if I had to do something that required the Door to be open I would have to disconnect the Wire from the Battery each time.

So I added a Toggle Switch in the Circuit next to the Vacuum Pump. After testing that I realized that I would have been better off with the Switch inside instead of under the Hood.

For the time being I am leaving things as they are until I find a suitable place to mount a Switch inside the Car. Not, in a hurry on that.
It works fine with the only issue being that while it takes little time to build up enough vacuum to unlock all of the Doors and Trunk it takes longer to build up enough Vacuum to lock the Doors and Trunk. (Perhaps my Unlocking System is where the Vacuum leak is.)

The easiest way to live with it is when you are in the Car and the Engine is still running pop the Door open enough to start the Vacuum Pump to let Vacuum build up and simply remain seated a bit. Turn the Engine off and get out of the Car and lock the Car.

The all Metal Door Switch is the one I added.

Diesel911 · #2 09-01-2013, 08:43 PM

Several Months after this thread I got around to trouble shooting the Lock Vacuum System and found one of the Vacuum Door Actuators leaking. I replaced that and My
And, I disconnected the Electric Vacuum System but left it in place; you never know when you might need it.
Lock system returned to normal.

That is until last night.
Although I was having no Transmission Shift or Braking issues I started off with the basics and wanted to see what My Vacuum Pump was putting out.

I plugged the Vacuum Gauge into the First Hose on the Main Vacuum Line and found I had intermittent Vacuum when I moved the Hose around.

The above info led to Me finding a crack in one of the Hose Connectors. With the connector replaced My Locking System returned to normal.

cooljjay · #3 09-02-2013, 03:30 AM

Neat idea and I have thought about doing the same....but like you my vacuum lock issue was an extremely simple one....but it took me at least two days to find it...and a headache....but it cost me nothing....I found out the vacuum supply line running through the door broke and who ever fixed it...used a half inch coupler...door open no vacuum leaks...door closed vacuum leaks....moral of my post, just get a strong cup of coffee and get out there and find the issue...

Stretch · #4 09-02-2013, 05:54 AM

I know you're keen on volvos but aren't W124 / 2nd gen W126 / W201 central locking pumps cheap where you are? I can get a used W201 pump for under 20 euros here. I realise location location location is everything - so I don't want to upset - just saying - and if it makes any difference shipping from me to you would have exceeded your $55...

Diesel911 · #5 09-02-2013, 10:31 AM

The Electric Vacuum Pump I bought was aimed at eventually replacing the Stock Vacuum Pump.
http://www.peachparts.com/shopforum/diesel-discussion/296397-electric-vacuum-brake-booster-pump-tested.html
However, that particular Vacuum Pump gets hot enough to blister you.
So in My case I was using a Vacuum Pump I already have.

I bought an electric diaphragm type Vacuum Pump that I am going to try at a later date to replace the Stock Vacuum Pump.

Concerning finding the leak in the Vacuum Lock System; if you follow the Manual and expose the Lines under the Carpet and that Plastic Shield you can identify what Line/s are leaking without too much difficulty if you use a Hand Held Vacuum Tester/Mighty Vac.
That will send you off to a specific area to check.

What surprised Me was I expected to find a whole bunch of rotted out rubber connectors. But, that was not the case; even after all these years the Connectors looked New.

Stretch · #6 09-02-2013, 12:22 PM

Ah ha a multi-tasking solution...

Smoker · #7 09-25-2013, 01:49 PM

Has anyone pursued the pump replacement further? I don't much care about doing it for central locking, I fixed mine, but I'm hearing sounds from up near the pump and it looks really old.

I'm thinking of making it an empty case and going with electric vacuum, I found one of the bigger saab units on fleabay

Saab 9 3 9 5 Vacuum Pump | eBay

Am I simple minded thinking I'd just need a vacuum cutoff switch set to about 20 and a relay?

Edit, this switch:

http://www.evparts.com/products/street-vehicle/brakes--dot/switches---street-vehicle/bk2785.htm

OM617YOTA · #8 09-25-2013, 05:15 PM

Check out my Toyota pickup repower thread. I did exactly this with a VW/Audi electric pump, a relay, and a vacuum switch. Works well, cost 1/3rd what a new mechanical VP would cost, won't destroy the motor if it fails.

Smoker · #9 09-26-2013, 08:14 AM

Well, I've jumped in with the Saab pump and a 'transmission lock up' 6 - 22 adjustable vac switch. I've got plenty of relays.

I plan to run it from switched power, so if there is a leak I'll lose central locks while parked just like the mechanical system, rather than run the battery down.

If it works during testing, what's the best way to neuter the pump? Just take the arm off?

Being a belt and suspenders type after testing I'll be getting a second pump to keep in the trunk spares bin.

whunter · #10 09-26-2013, 10:54 AM

Considering this alteration for a W124 300D.

.

Smoker · #11 09-26-2013, 11:23 AM

I'll post pic's and descriptions of the hardware used as soon as I get it all here and going.

My drive to work is about 60 miles so after a few short test runs the plan is to drive it there and stop a few times, pop the hood and zap the electric pump with the non-contact thermo to get an idea if I'm frying it.

Likely won't be until after next week, parts have to come in and I'm picky about wiring/mounting.

Quote:

Originally Posted by whunter

Considering this alteration for a W124 300D.

.

OM617YOTA · #12 09-26-2013, 11:33 AM

I just pulled the guts out of the mechanical pump. Yanked the arm and the piston. Put the empty case back on and pushed some RTV silicone into what was previously the vacuum port.

http://www.ebay.com/bhp/electric-vacuum-switch

http://www.ebay.com/itm/04-2004-AUDI-A4-B6-CABRIOLET-3-0-BRAKE-BOOSTER-VACUUM-PUMP-/151119190396?pt=Motors_Car_Truck_Parts_Accessories&hash=item232f67d97c&vxp=mtr

Those are the items I used. I didn't rubber mount my pump, and I wish I had. It's LOUD, easily audible over the diesel engine and straight piped exhaust. Hard mounting it turned my whole fender well into a speaker. People give the truck odd looks when it turns on.

The vacuum switch I bought switched the ground. Hooked key-on positive up to the positive side of the relay coil and the switched ground line from the vacuum switch to the ground side of the relay coil.

I build a vacuum reservoir out of a chunk of PVC pipe and some fittings. I usually still have vacuum in the system a couple days after it was used last, and the vacuum stored in the system is good for 2-3 brake uses after the pump has shut off.

With the intermittent use, even when it was 95 degrees outside, the pump never got too hot to touch.

Smoker · #13 09-26-2013, 11:43 AM

I dunno if we ended up with the same pump, likely it won't get hot. I was planning to use the stock vac tank (trunk), as it's still good. With your's in the truck it's doing less work, I'm using vac not only for PB but for tranny, door locks, seat back locks, climate... I still expect it's trivial use though for the pump.

I went with this vacuum switch. Don't know what others have used but it's the same was what is mentioned on EV forums.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemVersion&item=300916417793&view=all&tid=872910742020

Quote:

Originally Posted by OM617YOTA

I just pulled the guts out of the mechanical pump. Yanked the arm and the piston. Put it all back together and pushed some RTV silicone into what was previously the vacuum port.

The vacuum switch I bought switched the ground. Hooked key-on positive up to the positive side of the relay coil and the switched ground line from the vacuum switch to the ground side of the relay coil.

I build a vacuum reservoir out of a chunk of PVC pipe and some fittings. I usually still have vacuum in the system a couple days after it was used last, and the vacuum stored in the system is good for 2-3 brake uses after the pump has shut off.

With the intermittent use, even when it was 95 degrees outside, the pump never got too hot to touch.

OM617YOTA · #14 09-26-2013, 11:47 AM

Woops! Edited my post to include what I used, and replied to your PM.

I did use a different vacuum switch. Mine is going funky though, going to have to replace it I think. The specs show yours is beefy enough to use without a relay if you want, though the relay does make it easier to control key-on use.

Diesel911 · #15 09-26-2013, 12:13 PM

Quote:

Originally Posted by Smoker

Has anyone pursued the pump replacement further? I don't much care about doing it for central locking, I fixed mine, but I'm hearing sounds from up near the pump and it looks really old.

I'm thinking of making it an empty case and going with electric vacuum, I found one of the bigger saab units on fleabay

Saab 9 3 9 5 Vacuum Pump | eBay

Am I simple minded thinking I'd just need a vacuum cutoff switch set to about 20 and a relay?

Edit, this switch:

Brake Vacuum Switch

In My particular case I keep hoping to discover a cheap Vacuum Switch that is not $30 each; preferably in the $10 range. And, then there is the added Relay expense.

Please post a Pic of your Vacuum Switch and the Cost. The ebay site is gone.