Accident knocked a vacuum line loose - PeachParts Mercedes-Benz Forum

Cazzzidy · #1 10-24-2004, 03:07 PM

Hey guys,

After I was rear ended at high speed my transmission began shifting a lot harder. I also had a fluid leak ... which I feared was tranny fluid. Luckily one of the pressurized hydraulic fluid line nuts on the steering box had somehow loosened, so that was an easy fix.

I found a black vacume hose hanging lose in my engine bay. I don't have a digicam with me, so I can't post a picture, but I will do my best to describe it.

The hose that is lose is connected to a rubber Y. The Y stems from the side (not the top) of white plastic part (123 070 0046) on the rear of the injection pump. The second hose coming from the Y that was not dislodged goes up to the valve cover transmission shift linkage thingamabob. If it helps, the hose that was disconnected was kinda buried down low in the engine compartment towards the grill.

Need to know where this bad boy goes!

And a second question, where do I get a good vacume diagram? My repair manuals have nothing!

Thanks, Cassidy

rg2098 · #2 10-24-2004, 04:09 PM

Heres a link to a thread with all the diagrams you will need.

W123 and W126 Vacuum Diagrams

dieselbeagel · #3 10-24-2004, 04:41 PM

From ur post, I would say the end of the black line that goes to the trans is plugged onto a nipple on the trans modulator.

The trans modulator is close to the Neutral safety switch and in the vicinity of the transmission linkage.

Hope that helps.

Cazzzidy · #4 10-24-2004, 04:47 PM

Gosh, that is awesome.

However, I think my year must be peculiar or not covered, because my system is different from any of the charts listed. I wish I knew more about the location and purpose of the various controls.

Does any have any idea where the hose I described is supposed to go?

rg2098 · #5 10-24-2004, 05:09 PM

I'll take a few pictures of the lines on my car tonight and post them.

Cazzzidy · #6 10-24-2004, 05:34 PM

Thanks guys!

Okay,

So, a vacume line is hooked up to the green tranny modulator but is only pulling 10" at idle. I softened the shift up a bit with a 3/4 counter clockwise turn of the T. The shift is a little hard still ... I think the modulator needs more vacume.

Still no idea where the missing vacume line goes. I look forward to the pics RG.

Cassidy

mikemover · #7 10-24-2004, 05:46 PM

Quote:

Originally Posted by Cazzzidy

Thanks guys!

Okay,

So, a vacume line is hooked up to the green tranny modulator but is only pulling 10" at idle. I softened the shift up a bit with a 3/4 counter clockwise turn of the T. The shift is a little hard still ... I think the modulator needs more vacume.

Still no idea where the missing vacume line goes. I look forward to the pics RG.

Cassidy

If it's not the line to the tranny's modulator, then did you check to see if any of the other vacuum-operated systems on the car are not working as they did prior to the accident? How are the locks working? Engine shut-off? ACC system?.....

Mike

P.E.Haiges · #8 10-24-2004, 06:10 PM

Cazzidy,

The white part on the IP is a vacuum valve. It varies the vacuum to the transmission depending on how far the accelerator is depressed. There should be a tri connector somewhere in the vacinity. One lead connects to the vacuum supply, the other to the vacuum valve the third to the transmission.

One if the leads in the tri connector has a restriction in it. It should be marked by a plastic clamp on the exterior. This lead must go to the vacuum supply for the vacuum valve to vary the vacuum to the transmission.

If one of the leads is disconnected, it will affect transmission performance.

P E H

rg2098 · #9 10-24-2004, 06:44 PM

Hope these are the areas you need, if not tell me where you need them.

Cazzzidy · #10 10-24-2004, 11:39 PM

Thank you so much!

Man, the spirit of help around here is one of a kind.

The line that is disconnected is labeled "vents to passenger compartment"

Hmmm ... what does it do?

Everything else seems to be working fine. The tranny improved after I softened the shifts and adjusted the bowden. Now the car is having a hard time pulling past 70mph and kicking down at lower speeds.

psfred · #11 10-25-2004, 12:10 AM

The black line to the passenger compartment is a vent line, all it does is suck air in when the vacuum is vented off somewhere. It's there to pull clean air from under the dash rather than dirty air from under the hood, this keeps crud out of the vac pump.

I'd look for something else knocked loose or cracked -- the lines themselves get brittle, so does the plastic part in the middle of the main vacuum line to the booster. A crack there will lower the vac at the modulator, and you get hard shifts.

Also possible the jolt dislocated the valves in the tranny control valve, so that they aren't working right.

Get a MitiVac hand pump, it has a guage, and you can check. You should have 15" minimum vac to the modulator at idle, dropping instantly to 12" or so when you touch the accelerator, then dropping all the way to zero at wide open. Less vac will give harder shifts.

If the vac is OK, try replacing the modulator, it's cheaper than a tranny...

Don't forget to check that the hose is still intact to the modulator -- if the rubber connectors are bad, or the plastic line is cracked, the modulator won't see the same vac as the valve puts out.

Peter

phantoms · #12 10-25-2004, 12:20 AM

On some, that vent line has a small filter on it under the hood before it makes the trip through the firewall to the inside of the car where it ends and is open.

rg2098 · #13 10-25-2004, 06:40 AM

Make sure you have your tranny number when ordering a modulator if you go down that road. Apparently there are 5 or so different versions and i'm going onto number 3 now.