hey guys,

i have a vacuum leak and i found a plastic vac line that is not plugged to anything under the dash, above the steering column. the vacuum line comes in the dash through the firewall and when i follow the line, it has a filter on it, and continue till it ends at some thing im not sure what it is. i want to know what vac line is and where this thing is supposed to be.

right now, if i turn the key off, the engine keeps running, but if i reach under the dash and plug this mystery plastic van line and then turn the key off, the engine stops normally. my windows, sunroof and locks still work without the plastic vac line plugged...im stumped!!!

here are some pics...







thanks!

Year and Model???

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

The vacuum stuff make it appear to be an '85

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

That's a vent. It isn't supposed to be connected to anything. It lets air bleed into the vacuum system as needed. The line runs into the passenger compartment because (in theory) the air is cleaner there than under the hood. The filter is for additional cleaning of the air.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

yeah its an 1985 300d (good call JimmyL), thanks for the info jeremy, but if thats supposed to be open then dammit i need to find the other leak now to get that engine to stop running

Mine has the same thing. It is a 1985 300TD. The first time I came across it I thought I had pulled something loose and commenced to search under the dash to determine where it went. After the search I could find nothing close that it could have connected to so I just left it loose. The car ran fine so I figured it could not be causing damage.

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Doug

1987 300TD x 3
2005 E320CDI

There is a vac. pass/block switch on the end of the ignition switch assy. It is cam driven by the internals in the lock assy.... That passes vac to the cutoff valve on the very rear of the injection pump when the key switch is cut off....2 lines on it....one from the vac source and the other to the IP shut off valve....check these first....if you can pull a small vac on the IP valve with a hand pump...it should cut off engine if shut off valve ok...lines could be swapped around in engine bay causing the shutoff when you block the vent line....I think the vent line is just bleed for the transmission vac. controller on top of the IP...It should not affect the shut off function unless you have some leaks or low vacuum at the source....

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1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

Why not plug that line, and let the mystery leak be the bleed source?

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Paul
2004 E500 4matic; 72,000mi

That might actually work. The risk is losing track of which line is supposed to fill which function. All of the vacuum bleeds that Mercedes designed into the system are calibrated; the different color orifices that infest the vacuum system are all carefully chosen. A randomly chosen open line probably would not do what the correct plumbing is supposed to do. It probably would not be dangerous but might be very frustrating.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

i did that at first, i just taped the loose vac line shut, and when i went to drive it, the car was SOOOO slow and felt like it only had 10 horsepower, it was super sluggish, so i took the tape off and it ran fine

how is best way to check this, where should i go in to see the back of the ignition switch assy.?? thanks

Remove panel under driver side should give you some room to get to it....My experience is with a 1980 240D & 300D but yours should be similar.....looks like your shut off valve is working or it would not cut off and your key switch as well....so I would start by checking your main vacuum level at the vacuum hose between the brake booster and vac pump....there is lots of info on the Benz vac systems on this forum...just hard to find sometimes for your exact problem...the lines are color coded for the systems they operate...your main vacuum is probably ok unless you are having other problems...Tee a vac. gauge onto the vacuum reservoir line and see how fast it bleeds down after shutting off the engine....then start plugging lines to the different vac. devices to see where your leak is...it is just a step by step walk through the whole system sometimes before finding the leak or (leaks)....I had 3 leaks on the 240D ...trunk lock element...gas flap lock and master door lock....new rubber connectors fixed all of them...I changed every one of them on the whole system.....no more leaks...yet

Search forum for vacuum diagrams and that will help with vac system troubleshooting...this is really just plumbing work...

__________________
1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

excellent, thanks for the info

If you plug that vent line your 85 will downshift very hard.


85 300td
85 300d