My New Ride! Need help identifying a few things - PeachParts Mercedes-Benz Forum

harpua00 · #1 09-02-2008, 10:36 AM

As of about 2wks. ago I bought my first MB diesel and I've been searching and lurking on this site since; it's a 1985 300D with 230K miles, anthracite grey outside with black interior. No rust, and in general seems to have been relatively well cared for, though there are lots of nagging "little" things that no longer work. Actually, lots of them! The car runs and drives well, though it need front brakes and rotors. Central locking does not work. Gear shift lever seems loose and probably needs new bushings in the linkage and the 2-3 shift is a bit dragged out under heavy throttle. Sunroof doesn't work, neither does radio nor antenna. Oh and the drivers seat leaves my left cheek about 3inches lower than my right. Yikes, listing it all makes me realize I've got some evenings to spend on this car. But, despite all this I am in awe at the quality of the car (which because of all the problems, my wife finds very amusing)....for a 23 year old car it is outrageously solid; you drive over potholes and railroad grade crossings and can tell the sturcture is very rigid and really from this perspective the car feels like new. Oh, and I love the sound of the engine!

So, 4 intial questions:

1.) What is the lever that hangs off the back of the sunroof motor?

2.) If the radio (oem unit from the looks of it) won't power on and all fuses in the fuse box are good, does that mean the radio is dead? Is there any kind of code or sequence of buttons that need to be entered after battery was dead for a while? How about the antenna.....should the dash switch operate the antenna even if radio is not powered on? i.e. do I need to first fix/replace the radio before worrying about the antenna? Finally, the antenna connector in the trunk has two "extra" small, loose round pin connectors. One wire is blue/yellow and one is blue/green. They currently are not attached to anything, where should they attach? See photo

3.) I see a disconnected and plugged vaccum fitting on the firewall just above the oil filter housing. See photo. The fitting on the firewall is a yellow plastic connector or valve of some sort, the plugged fitting is a 4 way Tee. What is this?

4.) Final question. I hear a very loud continous screech at very light throttle in 2nd, 3rd and 4th gears between 2000-2400rpm. At first I thought loose belts, but the above conditions are the only times I hear the screech and I can make the screech happen every time just by using light throttle under the conditions described above. Other than those specific times, I never hear the screech (i.e. never at start up, or revving the engine as you would expect for loose belts). I'm wondering if maybe it's a vaccuum leak, not a loose belt?

Thanks!

Mark

LUVMBDiesels · #2 09-02-2008, 12:32 PM

First off -- Congrats on the purchase!

I will try to answer your questions although I am a W126 guy not a W123 person

First things first. Order a complete set of fuses and replace all of them. They might LOOK good, but be bad. In any case they tend to go bad from age. I just buy a new set each year and replace them all. The price is under $10 for a complete set and you will find that lot of electrical issues are solved.

#1 the lever could be the manual override. MB packs a manual crank with the car in case the sunroof motor dies while the roof is open. Does the lever come off? If it does that is the answer.

#2 The radio must be on before the dash switch will comtrol the antenna. The radio supplies the power to the antenna, the switch just controls how high it will raise itself. Once you replace the fuses, the radio might start working.
I am not sure about the extra wires on your connector.

#3 The vacuum line you have in your picture is the line that controls the central locking system. There is probably a leaky vacuum solenoid in one of the doors. It has been disconnected because ifthe vacuum is leaking, you will not be able to shut down the car with the key and the tranmission shifts will be harsh. Get a MitiVac and use it to pull some vacuum through the door lock lines. You can probably fix this pretty easily.

#4 That could be an issue. Are you SURE the belts are tight? If the belts are a little too narrow, they fall into the pulley grooves and will screech. I would get a set of belts as part of getting a new car. make sure that the belts are really 15mm wide. I got some belts from the dealer that were too narrow.

Other things that could cause a screech are bad bearings in the alternator, water pump or vacuum pump. The vacuum pump can detonate and kill the engine so if it is suspect, replace it.

Please use the search feature to research procedures on how to do the work.
Join your local chapter of the Merceded Benz Club of America MBCA.org as well as you will find members who have the same car as you and who have figured out what to do in most any situation.

winmutt · #3 09-02-2008, 01:42 PM

I dont think its the manual override, I think its the sheath for the sunroof?

harpua00 · #4 09-02-2008, 01:53 PM

good tip on the fuses. I hadn't thought of that, and car was not used for a few months before I bought it so maybe some corrosion has formed or whatnot. Only thing is the fusebox card shows other components on the same circuit as the radio and I recall mentally noting that those other listed components do work. I'll check it out regardless

1.) the mystery lever I don't think is the manual overide for the sunroof. The owners manual shows the white plastic hex bolt on the side of the motor as being the manual overide. The tire wrench seems to fit that hex bolt. The mystery lever sticks out the back and doesn't appear to be connected to anything (?). I can't remove it by pulling, can't push it further into the motor and because it does have a bit of a crank shape to it I rotated it a bunch of times but it doesn't seem connected to anything. That said, even rotating the hex nut doesn't seem to move sunroof, and pushing the sunroof button I hear no sound at all (no motor buzzing or humming or anything)

2.)check, good to know I need to get the radio going before worrying about the antenna. And those OEM radios didn't have any sort of reset sequence to power up specially after the battery was disconnected did they? The nighttime illumination on the radio does work when the headlights are on.

3.)thanks for the clarification about the central locking vaccuum line. I'll leave that for now then until I get the more pressing things done.

4.) The screech is so very specific with regards to engine speed and load. I'll see if it can be duplicated in drive but stationary with foot on brake. If so I'll get someone in the drivers seat while I look around with the hood open to see if I can narrow down where it originates. Detonating (imploding?) vaccuum pump sounds bad.......is this seriously a worry?

LUVMBDiesels · #5 09-02-2008, 01:56 PM

If the vacuum pump fails, it sends all sorts of nasty metal pieces right into the engine.

bgkast · #6 09-02-2008, 04:04 PM

That "lever" is a tube for the sunroof cabe to extend into when the roof is open.

harpua00 · #7 09-02-2008, 06:17 PM

Excellent, so I'm set with the plugged vaccuum tube ID, the mystery tube off the sunroof question and the issue of radio needing to be on before antenna will work.

Does anyone have any idea what my 2 "extra" round pin connectors are near the main antenna connector in the trunk?

Any common symptoms of a vaccuum pump about to fail? If you tell me it's normally a screech at light throttle under very limited RPM range I better take a closer look at that pump!

Thanks for all the great info!

Jeremy5848 · #8 09-02-2008, 06:38 PM

By the looks of your first picture (the sunroof motor tube), you have the original power antenna. It is possible that the antenna failed and someone removed pins from the connector to prevent a short circuit. That way, they could use the tape player or whatever is in there without blowing a fuse.

Here is the diagram for the antenna.

That should make it possible for you to put the connector back together. Looks like 4 pins in the connector plus a separate ground wire.

Color codes
BU = Blue
GN = Green
RD = Red, usually +12
BK = Black
BR = Brown, usually ground
GY = Gray
YL = Yellow

BU/YL [for example] = Blue with Yellow stripe

Jeremy

zeke · #9 09-02-2008, 09:55 PM

Where is the screech coming from. Does it do it with the AC off?

harpua00 · #10 09-03-2008, 09:16 AM

jeremy thanks for the radio diagram....I should be able to figure it out with this. Weird thing is I think the plastic connector already has 4 terminals, so with the two loose round terminals that makes 6 wires going to the antenna. Those two extra loose terminals appear to be wires that are all in the loom running back to the front of the car.....I don't think they were extra add-ons; they look original.

Zeke I don't think my A/C is working. In fact that's another issue to add to my "to be sorted out" list. I did a quick check and seems to me I get hot air blowing no matter where I position the temp control. Also can't seem to control which vents blow; always seems to blow from the windshild defroster vents. So to answer, the screech occurs even with interior HVAC off.

This AM I tried to see if I could get the screech to occur with car in D but stationary with foot on brake. The torque converter doesn't allow quite enough slip to get up to the 2000-2400rpm sweet spot for the loudest screech, or at least not with the light throttle that must also accompany the RPM's to dial in the screech spot. I could hear just a bit of the screech as I backed off the throttle after having brought up RPM's to almost 2000rpm.

remotemark · #11 09-03-2008, 11:44 AM

Mark, congrats on the purchase. I, too, recently joined the diesel team -- I bought an 84 300D almost two weeks ago. I agree, it is a fabulous car, solid as it gets. It's not as nimble or quick as my 124s, but it is, in my view, a gas (no pun intended) to drive. I have a couple of nagging issues, too, in particular, one we share:

4.) Final question. I hear a very loud continous screech at very light throttle in 2nd, 3rd and 4th gears between 2000-2400rpm. At first I thought loose belts, but the above conditions are the only times I hear the screech and I can make the screech happen every time just by using light throttle under the conditions described above. Other than those specific times, I never hear the screech (i.e. never at start up, or revving the engine as you would expect for loose belts). I'm wondering if maybe it's a vaccuum leak, not a loose belt?

I also assumed it was the accessory belt, and will change both belts shortly. But I have done some experimenting and noticed that it happens with the a/c (which works very well) off, too. So now I'm not so sure. I think I will have to get the back wheels off the ground to see if I can pinpoint the source of the noise on acceleration.

Does anyone have a sure-fire way to test a vacuum pump?

Thanks,
Mark

930dreamer · #12 09-03-2008, 07:40 PM

http://dieselgiant.com/index.html

Can the vacuum pump be rebuilt with the kit from diesel Giant?

toomany MBZ · #13 09-04-2008, 05:44 AM

In pic #3 there is a green with yellow stripe hard line, do you have a coupe?
Is there more than one yellow 2 into 1 check valve, like the one that is disconnected?

remotemark, on testing a vac pump, hook up a gauge, such as a Mity Vac to your main line coming from the pump, plugging off the other nipple, you should get around 25 Hg's, I think.

harpua00 · #14 09-04-2008, 08:51 AM

toomany MBZ, about the vac lines in picture#3:
- car is a 4 door sedan, not coupe
- I don't see any other 1-into-2 yellow check valves, other than the one that is disconnected
- From the disconnected yellow valve there are two yellow vac lines that go to a connector at the firewall. Looks like 5 or 6 vac lines all connect here and go through the firewall. It's pretty dirty in there, but it looks like there may be one unconnected nipple in the middle of that connector. Hard to tell for sure though until I clean it up, and I don't see any stray lines nearby that look like they should go there.

toomany MBZ · #15 09-04-2008, 04:03 PM

Quote:

Originally Posted by harpua00

toomany MBZ, about the vac lines in picture#3:
- car is a 4 door sedan, not coupe
- I don't see any other 1-into-2 yellow check valves, other than the one that is disconnected
- From the disconnected yellow valve there are two yellow vac lines that go to a connector at the firewall. Looks like 5 or 6 vac lines all connect here and go through the firewall. It's pretty dirty in there, but it looks like there may be one unconnected nipple in the middle of that connector. Hard to tell for sure though until I clean it up, and I don't see any stray lines nearby that look like they should go there.

OK, that one disconnected check valve goes to your door lock system. A coupe has another one, and the vac line is blue in color, I remember now.
I imagine there is a leak somewhere, and plugging off the door locks will remove said leak, and you can shut the engine off with the key.
The brown vac lines go to the starter switch.

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