Replacing vacuum line from engine to drivers door - PeachParts Mercedes-Benz Forum

rosenfe · #1 03-22-2018, 10:40 AM

My 82 240d has a torn vacuum line thus no vacuum to door.Has anyone runs line from engine to door? Any tips and is there a source for the vacuum hose. I can splice pieces together if not.

Diesel911 · #2 03-22-2018, 11:24 AM

Any vacuum hose that fits tight on the plastic tubing will work if there is room to pass it through the Door. I am not 100% sure that where the door hinges won't pinch off rubber hose or silicon vacuum hose. You can splice.

This is not a job I have done before.

Note there is plastic vacuum tubing available but I doubt if you can find the colored tubing.

tyl604 · #3 03-22-2018, 04:52 PM

The clear flexible tubing that you find at any Ace Hardware works fine for a splice in most places. Do not get rid of your original tubing; splice it when possible.

rosenfe · #4 03-22-2018, 07:24 PM

I ended up going to Mercedes and they had the line in rubber,5$ a meter. I was able to use portion of hard line to get through firewall grommet into engine compartment and also threaded rubber line with old plastic vacuum line through the door. It worked and holds vacuum. I now have functioning door locks

tyl604 · #5 03-22-2018, 08:12 PM

Good to go.

Junkman · #6 03-24-2018, 06:16 PM

I've used air brake hose before on other applications. It's pretty tuff stuff & there are plenty of metal connectors available if needed and you don't want to use some kind of rubber hose for the joint.

Some of it is plumbing a fuel pressure gauge on the Cummins and it has been installed for several years. I periodically check it and never a bulge, crack or leak.

vwnate1 · #7 03-25-2018, 08:22 PM

They occasionally get cracks and weep vacuum where they flex at the doors, just go to the self service junk yard and scavenge the pristine, flexible yellow tubes from underneath the passenger side floor mats ~ plenty long enough and never crispy/rotted .

1983/300CD · #8 05-23-2018, 01:37 PM

I have the same question. I need to thread a new line from the engine to the door. I have some new plastic line and I was thinking of somehow connecting it to the leaking yellow line and pulling it through.
Does anyone have suggestions on which direction to go?
Is access available if I remove the dash?

vwnate1 · #9 05-23-2018, 10:28 PM

BEFORE you go tearing it ll apart you need to test to be 1,000 $ SURE the yellow plastic pipe is leaking by opening up the door and capping it off where it meets the master control valve then testing the correct yellow pipe under the hood where it pokes out the firewall .

There are _two_ yellow plastic pipes and the one with the blue stripe goes directly to the vacuum resivoir in the trunk and takes some time to show vacuum on the hand pump testing tool .

You _can_ reach these by sliding the driver's seat all the way back on _both_ adjustments but it's not fun nor easy and the pipe going from the firewall to the door is two pieces, having a white/black pot near where it enters the passenger cabin .

Messing with this is a serious job, make SURE you've isolated the problem before making things far worse .

Disconnect the yellow three nipple vacuum check valve and use NEW rubber hose bits when connecting the test tool to the solid yellow pipe .

I've just gone through all this on another of my W123's, it's a big PITA but not properly diagnosing where the vacuum leak is, is far worse .

1983/300CD · #10 05-24-2018, 08:45 PM

Yeah, it shuts down nicely when the yellow line is golf tee'd. I will hook up the reservoir line just to test that too.
I just am really confused as to why pushing the dome light switch in the jamb worsens the leak.
I think I remember two yellow lines running behind the driver's side kick plate in front of the door. That might be a good place to get in.

vwnate1 · #11 05-24-2018, 08:51 PM

That's because the seat back locks are leaky, disconnect the BLUE plastic vacuum pipes at the firewall from the vacuum source .

I bet there's nothing wrong with your central locking circuit's yellow plastic pipes .

1983/300CD · #12 05-25-2018, 12:01 AM

It's the switch in the door that exacerbates the vacuum leak, not the switch on the seat, and the blue line has been capped under the seat for a while now. But I'll cap it in the engine compartment too just for confirmation.

ROLLGUY · #13 05-25-2018, 11:12 AM

Quote:

Originally Posted by 1983/300CD

It's the switch in the door that exacerbates the vacuum leak, not the switch on the seat, and the blue line has been capped under the seat for a while now. But I'll cap it in the engine compartment too just for confirmation.

I mentioned it in your other thread about this problem, the switch activates a vacuum valve for the seatback arrestors. There is probably a vac leak there. I believe it is behind or near the glove box. Isolate that part of the system, and you may find the problem.

1983/300CD · #14 05-25-2018, 02:11 PM

I removed the 5-way connector and plugged in a 3-way.
I then plugged in the orange/brown shut off line.
Then, I plugged each line into the 3-way and checked that circuit.
They all shut down.
Did I mention the problem was intermittent? After moving the lines after an oil change, it will run on.
So now I have a new theory:
My 5-way connector isn't cracked, but it isn't exactly gripping onto the lines either. Maybe air is slipping in when the hoses are in the wrong position.
The release from the draw of power of the dome lights and whatever else is on that circuit allows the engine to chug on another little bit.
What do you think?
In any case, it's fixed now just by messing with the 5-way. It takes maybe 1/2 second after turning the key before it shuts down, but that's okay.

kuene · #15 05-25-2018, 03:01 PM

you can make a new 5-way by mating a 4-way to a 3-way. Otherwise it's prob hard to find a new dedicated 5-way.