More 1985 300DT Questions for you pros....

[wordmanjay]

Continuing to bring the maintenance up on my '85 300DT. I've run into a few more questions. Here goes:
1. What is the correct name of the 3-pronged switch on top of my valve cover that is activated by my accelerator mechanism?
2. Where can I get one of those 3-pronged switches?
3. Smog hose? What is the correct name of the hard plastic tube that connects my "breather hose elbow"(coming from the top of the air case) to the rubber elbow coming out of the top of my valve cover.
4. Where can I get one of these "hard plastic tubes"? I can only find a Cali type online. Mine is a "fed" type- plain curved hard plastic tube.

Diagnostic question:
I'm getting a lot of oil coming through that "hard plastic tube" and making a bit of a mess inside my air filter.
My mechanic (a non-diesel guy) said that too much oil coming back through that tube indicated a faulty PCV valve. Hmmmm.
Previously, someone here suggested I take the top off of the little cannister inside of the air case and seal it back down with some sealer-he said that may prevent oil from soiling my air filter. Hmmmmm.
1. Does that 3-way switch have anything to do with this? It's cracked and barely hanging onto the male end of the connectors.
2. Does this engine have a PCV valve?
I kinda need some elaboration on this topic.
As a side note, just on the outside chance it's related- this car was hit in the back end and the fuel spout area got crunched(enough that the fuel door is permanently open). The vacuum issues include no power door locks, faulty opening and closing of vents, and manual engine shutoff (under the hood). Also, the glowplug light on the dash doesn't come on anymore(that may be a separate issue).

Please help. I'm sure you will. You always do.
Thanks.
Jay

Originally Posted by wordmanjay

1. What is the correct name of the 3-pronged switch on top of my valve cover that is activated by my accelerator mechanism?

Waste Of Space is their adopted name, 3/2 valve is their official name.
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2EW05KXCY2EW05L68D&year=1983&make=MB&model=300-DT-001&category=All&part=Vacuum+Valve

2. Where can I get one of those 3-pronged switches?

Getting rid of them is better than replacing them. They only control the EGR and your engine will run better if they are gone completely.

3. Smog hose? What is the correct name of the hard plastic tube that connects my "breather hose elbow"(coming from the top of the air case) to the rubber elbow coming out of the top of my valve cover.

Crankcase breather hose, see below.

4. Where can I get one of these "hard plastic tubes"? I can only find a Cali type online. Mine is a "fed" type- plain curved hard plastic tube.

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=2EW05KXCY2EW05L68D&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=B2010-21290&application=000037398

I'm getting a lot of oil coming through that "hard plastic tube" and making a bit of a mess inside my air filter.
My mechanic (a non-diesel guy) said that too much oil coming back through that tube indicated a faulty PCV valve. Hmmmm.

Hummm. Sounds like your mechanic does not work with diesels often, there is no PCV valve.

Previously, someone here suggested I take the top off of the little cannister inside of the air case and seal it back down with some sealer-he said that may prevent oil from soiling my air filter. Hmmmmm.

Thats what you should do.

1. Does that 3-way switch have anything to do with this?

No. Those valves only deal with the EGR.

2. Does this engine have a PCV valve?

See above.

I kinda need some elaboration on this topic.
As a side note, just on the outside chance it's related- this car was hit in the back end and the fuel spout area got crunched(enough that the fuel door is permanently open). The vacuum issues include no power door locks, faulty opening and closing of vents, and manual engine shutoff (under the hood).

That can easily cause vacuum problems. There are several vacuum tubes going to the trunk lock and fuel lid lock that could be damaged by an impact. Any leaks in them will affect the whole door lock system.

[Cervan]

get rid of all that egr crap...

[winmutt]

Hardly "waste of space" in an 85. This is the electronic linkage sensor plug. Is it broken?

[JimmyL]

Originally Posted by ForcedInduction

Waste Of Space is their adopted name, 3/2 valve is their official name.
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2EW05KXCY2EW05L68D&year=1983&make=MB&model=300-DT-001&category=All&part=Vacuum+Valve

Getting rid of them is better than replacing them. They only control the EGR and your engine will run better if they are gone completely.

I think this is one of those 1985-only things he is talking about Forced. There is an electrical switch on top of our valve covers. I thought it was something about cutting off the AC under max acceleration {heard that somewhere}.

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=27R1AUDQC2EW0NZF6O&year=1985&make=MB&model=300-TDT-001&category=C&part=Throttle+Microswitch&appEngines=_any

Here is what it looks like. {pic was after I first got the wagon. Engine looks embarrassing}

Originally Posted by ForcedInduction

Crankcase breather hose, see below.

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=2EW05KXCY2EW05L68D&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=B2010-21290&application=000037398

There are replacement hoses that are flatter for your crankcase breather. In the pic above is a cracked one I replaced of that style, and I went back with one just like it. I think it is a newer design.

**edit**
here is one

http://**************.com/node/693
[if the link doesn't take you to it, search "breather" from their search box

[Jeremy5848]

If this truly is an '85, the only switch on top of the valve cover is a microswitch that talks to the Klima relay. As Jimmy noted, when you floor the accelerator, the microswitch tells Klima to de-energize the clutch on the a/c compressor, thus giving the wheels a little more power. This switch is probably available only in a junkyard or a dealer.

The hard plastic breather hose should be available here, from FastLane -- click "Buy Parts" at the top of this page.

This car does not have a PCV valve. There is a mechanism inside the valve cover that separates liquid oil from crankcase fumes; it doesn't always work as well as we would like and some oil does get into the air filter box. For this reason, Mercedes designed a drain into the air filter box, to allow accumulated oil to flow through a tube and back to the oil pan -- it runs parallel to the turbo oil drain pipe. If this drain is plugged or otherwise not working correctly, it will make a mess inside the air filter box.

The fuel door has a vacuum-operated lock. If it is damaged, it can cause air to leak into the vacuum system and you will have all of the symptoms that you describe -- no door locks, etc. Find and plug the vacuum line at the fuel door and see if that helps.

The glow plug light could be caused by (a) bad bulb, (b) bad glow plug(s), (c) bad glow plug relay. First, check the 80 amp strip fuse in the glow plug relay (it's on the left inner fender behind the headlight). Pull the cover off and you will see what looks like a strip of aluminum at one end. That's the fuse. Second, check the glow plugs by unplugging the heavy six-pin cable from the relay and measuring with an ohmmeter from each of the six pins to a good ground like the valve cover. You should get a very low reading -- about 1 ohm or so. If you get a couple hundred ohms for any of the glow plugs, they are bad. Replace them. If the glow plugs are all good, check the bulb in the instrument cluster. If nothing else, it would have to be the relay itself (least likely, IMHO).

What else?

Jeremy

[winmutt]

The flat hose is the old. depricated one. I was totally unaware of the fuel door lock good to know. As far as the switch I would bet the fastlane linked one is the same thing, in newer models used for ASR, and older for the klima cutout.

[85chedeng300D]

I'm not sure but if I have to guess, that micro switch is a safety switch to prevent the AC compressor from spinning too fast at full throttle while the clutch is engaged, hence that switch disengages the clutch at full throttle. My Mitsubishi Galant has that feature too....

[Jeremy5848]

Originally Posted by 85chedeng300D

I'm not sure but if I have to guess, that micro switch is a safety switch to prevent the AC compressor from spinning too fast at full throttle while the clutch is engaged, hence that switch disengages the clutch at full throttle. My Mitsubishi Galant has that feature too....

An interesting thought. I had not considered the challenges that accompany allowing the customer to operate the clutch without supervision all sorts of bad things could happen. Someday when I get the opportunity to see a late model manual shift W123 car I'll have to look and see how it is wired.

[85chedeng300D]

Originally Posted by Jeremy5848

An interesting thought. I had not considered the challenges that accompany allowing the customer to operate the clutch without supervision all sorts of bad things could happen. Someday when I get the opportunity to see a late model manual shift W123 car I'll have to look and see how it is wired.

By the way, before you get too far into that manual shift wiring thing, check your AC compressor if it has a clutch that allows you to shift into 4 or 5 gears, and don't forget the Reverse?
I don't know if it's just me or.........

[wordmanjay]

You all really supplied me with the info I needed.
Jeremy, I did exactly what you said- I went back by the fuel nozzle, found the bladder (smashed in the accident), pulled the lines going to the fuel door and the back lock, stuck two golf tees in the ends, and.........
I DON'T HAVE TO OPEN MY HOOD TO SHUT OFF MY CAR!!!!!!!!!!!
MY POWER DOORS WORK!!!!!!!!!!!!!!!!!!!
MY VENTS OPENED AND CLOSED PROPERLY!!!!!!!!!!!!!!!!!!!!!!!!!
I can't tell you how stoked I am. That may seem incredibly juvenile, but I'm digging working on this thing.
So next up is fixing the back window- it went down and now I don't even hear the motor trying- had to take the door apart at a remote locale, take out the screws and nuts holding the whole door motor apparatus, and push the window up by hand..... got any advice/links before I start hunting?
Oh, and of course I have another thread open about hunting down my windshield washer issue.....
The real fun will be when I get the back end straightened- the frame was bent and I'm hoping I don't have to replace too much. It drives very well, albeit with a few peculiar sounds in the back end. I have favors to call in on the frame straightening and bodywork, so I'm more concerned with running up the tab on any parts I have to replace underneath. Bumper and matching taillights is all I need up above and I have a line on reasonably priced replacements. More fun with that later. I'll see if I can dig up a pic.
Thanks.

[wordmanjay]

The before.....

[Jeremy5848]

Congrats! One of the nice things about older Mercedes is you can work on the things . . . take them apart, fix them, put them back together. It's a lot of fun.