oil in vacuum system-yikes! - PeachParts Mercedes-Benz Forum

Deanna · #1 10-04-2008, 02:02 PM

Well, my 82 240d has been running well for a few months, so I suppose it's time for a problem again. I just replaced my speedometer cable and while doing so, unplugged a vacuum line that shuts off the engine. This resulted in me tinkering around a bit, trying to fix the problem, and discovering that one of the vacuum lines (I think, from the diagrams, that it's a vacuum line coming out of the vacuum control valve just to the drivers side of the valve cover, near the firewall) had oil in it. My hunch is that this is a pretty bad thing.

I pulled the line off and plugged it. This resulted in a drastic loss of power, especially on the uphill. So I plugged it back in, but I'm pretty worried about it.

The only noticeable problem I've been having before I discovered this was the brake light coming on when I brake. I now assume that this has to do with the brake boost.

What's going on? Is there a diaphram in the vacuum control valve that could break and allow oil into the system? Help! I don't want to keep driving it and really f* myself over.

THANK YOU!

Deanna

toomany MBZ · #2 10-04-2008, 02:43 PM

What color line has the oil in it?
I understand the VCV is for the transmission, so you should not have a performance problem associated with that.
There is a hard vac line, brown,, via a soft black rubber connector, that goes just below the VCV, and attaches to the shut off valve. I had an oil in that vac line problem, and replaced the shut off valve.
That would not have any effect on performance either.
Does the car shut off with the key?
These engines do not produce vacuum, so they engineered a pump to run all the systems.
I cannot figure out any performance related issues connected with vacuum, or lack thereof.
Good luck.

Cervan · #3 10-04-2008, 03:30 PM

if the oil is black then its coming from the shut off valve on the injection pump, if its red then its coming from the modulator on the transmission.

Deanna · #4 10-09-2008, 12:01 AM

The oil is black, but I'm not having any problems shutting the car off. Shuts off just fine.

Noticed today that it smelled like oil when I was driving it and the brake light is still coming on (I've totally overhauled them just a year ago and the fluid is topped off). Is there anything else that could be wrong here?

I'll go out in the morning and check the color of the lines, but I think they're black.

Cervan · #5 10-09-2008, 01:08 AM

Quote:

Originally Posted by Deanna

The oil is black, but I'm not having any problems shutting the car off. Shuts off just fine.

Noticed today that it smelled like oil when I was driving it and the brake light is still coming on (I've totally overhauled them just a year ago and the fluid is topped off). Is there anything else that could be wrong here?

I'll go out in the morning and check the color of the lines, but I think they're black.

Just because its leaking doesnt mean your car still wont shut down correctly, a pinhole leak will still allow the car to shut down correctly but will draw oil into the vacuume system. The shutoff valve is the only place black oil can come from.

Cr from Texas · #6 10-09-2008, 01:08 AM

I've seen this too.
My theory: If the shut off valve has ever gone bad, you get oil in the vacuum line. Unless it is all removed, there will be a slug (1/4" or more) that is constantly moving through the system as air is pumped out and restored to the lines. It will eventually end up at a rubber connection, POD diaphram, etc. where it begins to deteriorate the rubber and then you find it.

cdplayer · #7 10-09-2008, 01:15 AM

My first Benz was an 80 300CD. I had oil in some of the vac lines as well.
Didn't know much about these cars then. Then one day the oil belched up into the oil breather and bled down the outside of the breather assembly.

Turns out the culprit was the vacuum pump diaphram. Developed a pin hole that just kept getting bigger as time went by.

May not be your problem, but just a thought.

MBeige · #8 02-23-2009, 10:59 PM

I'm having this problem with my 83 300D, there is oil in the vacuum line but alas, since I installed the filter between the yellow check valve and the brake booster line (2nd nipple), I saw the oil leak. Shuts off well enough for me to do a second take.

Should I DIY this or have a mechanic do it instead? I'm very apprehensive from hearing others installing it wrongly and have the engine run away.

Is there a DIY link for the shut off solenoid? Thanks

compress ignite · #9 02-24-2009, 12:36 AM

mbeige,

You're gonna have to invest some time at the Advanced Search part of the
Forum.(I do not know of a link to a Vacuum Shutoff Valve R+R for the 617.
BUT It's not that hard to do.)

deanna,

cervan has correctly diagnosed your MB's malady.

I suffered this affliction on the 300SD.'Bad shutoff diaphragm at the IP.
Vacuum pulled engine oil up into the HVAC (Heat+Air) system AFTER
going up to the Vacuum shut off switch at the Ignition Key.
Messy...Took Everything apart and inspected/cleaned.Installed a small
clear inline Bosch fuel filter in the Ign. Switch to ShutOff valve hose to
Alert to future diaphragm failure.

toomany MBZ · #10 02-24-2009, 05:43 AM

^^Agree with replacing the shut off valve as pretty straight forward. Note the orientation of the old valve, and install the new one the same way, you'll be fine.

MBeige · #11 02-24-2009, 03:17 PM

Quote:

Originally Posted by toomany MBZ

^^Agree with replacing the shut off valve as pretty straight forward. Note the orientation of the old valve, and install the new one the same way, you'll be fine.

How do I know if I'm installing it correctly or not? I know if I install it the wrong way I can lose my engine.

And how do I remove the oil that got in the vacuum lines (presumably to the ignition switch vacuum element and back out the firewall into the 4-way connector)?

Is there enough room for the new shut off valve between the IP and oil filter? I don't want to start this and get caught in the middle.

Thanks.

toomany MBZ · #12 02-24-2009, 07:42 PM

Here's a pic of my failed shut off valve. Note there are three gaskets, a metal one sandwiched. The circle to the right is the nipple for the vac line. You'll also note the hook on the end that goes into the IP. Just put it in, and install the four screws you removed first, plug in vac line. Note that orientation. The nipple will be in the same position.
I forget if I tried to spray something in the line to clean out the oil.

MBeige · #13 02-25-2009, 03:09 PM

Thanks, so I need two of the new gaskets and I assume it already has the old metal one in there?

When I hook up the shutoff valve, will it be pretty obvious or will I snag a few things inside the IP considering it's a tight squeeze and it's hard to see inside.

I may remove the VCV before the shutoff valve to gain better access to it, unless it's a bad idea...?

toomany MBZ · #14 02-25-2009, 07:51 PM

Quote:

Originally Posted by MBeige

Thanks, so I need two of the new gaskets and I assume it already has the old metal one in there? Yes.

When I hook up the shutoff valve, will it be pretty obvious or will I snag a few things inside the IP considering it's a tight squeeze and it's hard to see inside.

I may remove the VCV before the shutoff valve to gain better access to it, unless it's a bad idea...?

It just slides in, I can't remember if I had to hook it on something, but I doubt it.

I cannot remember, either, if I removed the VCV, but am leaning toward, yeah.

Just make sure you put the square ring on the OUTSIDE, of the valve when re-installing. Guess what I did! That screw furthest away is difficult to get started.

MBeige · #15 02-26-2009, 01:51 AM

I've decided to take this to my mechanic instead, and leave it to somebody who has done it before than try this first time and learn the hard way. But I'll take all your input in mind, and truly appreciate the help.