It's under the hood, right in front of the passenger side.


And in this area, I am hearing a hissing sound that seems like a vaccuum leak or something. There are 2 grey 1/8" thick tubes, one that is clearly sucking and if I cover it up it stops, and another tube that looks like something is broken from it and wants to be connected to the other one. The tube making the sucking sound heads toward the middle of the passenger compartment. The other tube I can't really tell where it goes.


Does anyone know what that might be for? Is it important? Any idea how I can reconnect them if they should be?

Thanks in advance for all your expertise!! :-)

the twin towers should be the duo-valves for the AC

the single tower with gray tube appears to be the top mount for the shock.

i dont have a 4matic to look at until the coming weekend. anyone else?

I don't think it's 4Matic related as I have the same line on my non-4Matic E320. Hard to tell where it's going. One end slips down behind the engine bay partition and the other turns south thru a small opening in the inner fender.

On the other hand, I don't think any vacuum leak is a good thing. Mine looks like it's designed to be disconnected at that point (test?). Probably dealer only part unless you want to try some small metal tubing from a hobby store.

Okay - so it sounds like your grey tube is connected all the way through.

I'll have to get that part in the middle then - the piece that looks like it can be disconnected for test must have broken apart in mine. Which of course concerns me since only the dealer does work on my car.

I also realized that the nice MB plastic engine cover was cracked off toward the back of the engine, and the dealer mechanic must have done that too, cuz I'm almost positive it was perfect before.

Yes, mines intact.

When it comes to plastics, I'm slow to accuse. It seems, from my experience, that at about 10 years many plastics begin to self-destruct. Ozone, UV and heat seem to be the primary enemies.

After thinking it over a bit more, could it be a check-valve or filter? Design seems a bit elaborate for just a connector and perhaps a test point would be some sort of 3-way so that one of the other connections would not have to be disconnected?

In any event, good luck.

This vaccum line is for the A/C Vent, you can solve this problem by this way! it's broken in my car some months ago, this way you dont need to cut the factory terminal

Fabio Daniel

part of the ac system.They operate the hot water flow for the heating system.
Running in conjunction with the ac system.
If it matters in the soup mix of things