A few years ago, I heeded the warning of a MBCA Technical Article and placed a cheapo fuel filter on the vacuum line that runs from the main line to the yellow 3-way valve on my 82 300D. The purpose of the filter would be to catch oil from potential vacuum pump diaphragm failures early enough so that oil wouldn't get into the various vacuum powered accessories. Well, FFW a few years and a few forum searches later. I've determined that I need to install 3 more filters on the various vacuum lines under the hood. I would place them in the following locations.
1. On the vacuum line that branches off from the main line and runs straight to the transmission VCV (there is no branchoff to the EGR since I have my EGR permanently disabled).
2. On the line running from the "ignition switch" to the shutoff valve on the IP.
3. On the vent line that runs to the cabin (the filter in that location would keep dust and debris from getting into the system from the under dash environment).

So, what do you say, is adding the extra 3 filters a good idea, or is it just overkill from a guy who's just itching to do some sort of wrenching, albeit cheap and not at all time consuming. Hopefully this won't result in responses as inflammatory as those found in an oil thread.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

why not 1 filter right after the pump?

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-->1971 mercedes 220D; 617 951 engine, 4 speed

The shutoff valve can also leak oil.

Well, there's a reason to add a filter at the shutoff valve!

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I would even go so far to suggest you try to position these horizontal to provide a place for the oil to pool and more easily be seen. I've had some trouble finding the right connectors to connect the two different sizes.

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/showthread.php?t=296386

I don't know how the vacuum pump works, but if it has a diaphragm in it that can malfunction, how does the oil travel away from the vacuum pump when air normally travels toward the pump?

If the diaphragm you're talking about is the fuel shutoff valve, then a filter between the shut off valve and the key switch would be a good idea.

If you're trying to protect the pump from dust, then a filter at each branch would be needed, but how often to vacuum pumps fail?

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

You should install 3 filters.

.1 Coming off the main line from the vacuum pump to the brake booster. Choose one of the lines that tap off the main line. This will inform you of a vacuum pump leak.Yes the vacuum pump is a diaphragm vacuum pump. The door vacuum pump reserviour which holds vacuum for the door locks, the check valve can leak and pull oil into the lines from the main vacuum pump.

2. The shutoff valve. the interior of the IP is bathed in oil. So if the diphram leaks oil it will get into the shut of lines.

3. The transmission line. The transmission modulator could leak and allow transmission fluid into the system. This one I have not done, but it is a potential fluid leak area.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Re: #1, So it's just enough to place a filter on one of the lines coming off of the main line and not both lines that come off of the main line?

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

IMO:
It can NOT hurt, makes failure diagnosis easy, and reduces or eliminates cleanup.


"Hen's tooth" 1985 300D vacuum filter dark black
http://www.peachparts.com/shopforum/showthread.php?p=1265296

x2. It's not enough difference to matter but I think my key shut off has a little more delay with the filter. Makes sense, larger volume to evacuate. But after cleaning out oil and replacing the valve at the IP and the key switch, I'll never be without the filter.

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/showthread.php?t=296386

One of the filters saved me by telling me that the shutoff valve had a torn diaphragm (leaking oil as predicted).

I was also contemplating on adding a filter to those mentioned areas.

The EGR lines also caused the filter to turn black (soot).

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http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg

Im sold, definitely worth the small trouble of cutting the lines and putting the 99 cent filters in.

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-->1971 mercedes 220D; 617 951 engine, 4 speed