Vacuum lines rebuild 1985 300d - PeachParts Mercedes-Benz Forum

Mahoney'sMercede · #1 05-16-2014, 06:13 PM

Hi,
I recently bought an old, slightly rusty 1985 300d previously owned by a punk kid who destroyed the vacuum line system. My turbo no longer kicks in and the car takes 60 sec. to get from zero to 60 Mph. My research points to insufficient vacuum, but if anybody thinks differently please tell me.
I want to rebuild the system but need to know What sizes of line, kinds and quantities of junctions, and what other things i will need, also where to find them online.
Also my passenger rear window very occasionaly will work great but otherwise does not respond to the front or rear buttons.

Answers would be great. My haynes manual is on the way so there is hope.

-CMahoney

JamesDean · #2 05-16-2014, 06:25 PM

Hi CMahoney,

Welcome to the forum.

The vacuum system is largely unrelated the turbo's power output. What might be happening and is very common is that the boost pressure line coming off the back of the intake manifold is blocked up with soot or could be missing depending on how much of a punk the kid was....

Check that line out and see if its plugged up. Post up pictures of the engine bay if you can that way we can look at just what was done and maybe even draw up what you should do to correct it.

-Kris

uberwasser · #3 05-16-2014, 06:45 PM

Second the engine bay request. I can post pics of my '85 engine bay for comparison on vacuum routing (system is 100%). Did he pull vacuum lines out of the body, too, or just leave those unplugged?

The rear window sounds like a flaky motor, the brushes inside are probably worn. Or, a broken wire inside the hinge area. I think you can rule out the switch at least. I say that, because it acts that way on both switches so it's not just a flaky front switch, which can happen too.

To confirm this you can test the wiring at the motor by pulling the back off the rear switch to reveal the wires. Use your tester to find which one gets 12v when you toggle the front switch. If it is getting 12v, but the window motor is not moving, it pretty much confirms the motor. The motor can be replaced separately from the regulator. Good used ones are on eBay or at your local scrapyard. You can see this link to see how the wiring looks behind the switch:

http://www.ifixit.com/Guide/Mercedes+W123+Power+Window+Regulator%2C+Rear+Replacement/20428#s56347

Mahoney'sMercede · #4 05-19-2014, 09:38 PM

Thank you kris,
I have already checked the boost line and banjo bolt and they are both very clean all the way to the switchover valve on the firewall and down to the engine.
One new thing ive found is that the EGR valve on the valve cover leaks a lot of oil into the air filter which leaks directly down into the turbo. There's a metal tube which connects into the underside of the air filter housing and i think it's meant to redirect oil, however it does not attach to anything, it only ends near the oil pan. I think its meant to drain into the pan but im not sure.

Mahoney'sMercede · #5 05-19-2014, 09:42 PM

I am going to take apart the rear door and test the wires to the window motor, and i bet ill find them frayed at the door hinge.
Thanks uberwasser.
If I can get pictures of the engine bay uploaded i will.
The punk didnt mess with the vacuum line in the cab, only the engine lines. He disconnected some and mixed up others in an attempt for more power.

Thanks
-CMahoney

toomany MBZ · #6 05-20-2014, 08:05 AM

The item you refer to as the egr valve on the cam cover, I believe you mean the breather hose for any blowby to discharge into.

At the bottom of the of the air cleaner housing, there is a drain for the excess oil to get back to the oil pan.

#48 in the cutaway.

The last shot shows the only layout of the 85 under hood vacuum system I have, it shows what to delete to bypass the egr system.

Mahoney'sMercede · #7 05-22-2014, 10:03 AM

I'll take your word for it, thanks for the info. What are the advantages of bypassing the egr system?

JamesDean · #8 05-22-2014, 10:16 AM

The EGR's only function is to recycle exhaust gasses back into the intake. On a diesel the exhaust gasses are full of soot as a result of the burning diesel. This soot eventually lines the intake manifold and the EGR valve and is just generally not helpful to the running of the engine. Its sole purpose --that I am aware of-- is emissions.

Mahoney'sMercede · #9 05-22-2014, 12:06 PM

Thanks James Dean,
If I do rebuild the vacuum system where online can I buy the vacuum line couplings and splitters that i'll need for the engine bay vacuum system. What else are the common problems for a slowly accelerating mercedes, seeing as the line off the intake manifold is spotless.

I have pictures on my computor, but how do i upload them, all the thing says is the url?
-Mahoney

toomany MBZ · #10 05-22-2014, 09:11 PM

Agreed, the egr system is trying to have you burn hot carbon monoxide as a opposed to cold, relatively, oxygen.

Click on "Post Reply" your computer will open with a box that has manage attachments, click on that, a box will open allowing you to decide from where on your computer to select from, click on the photo section.

JamesDean · #11 05-22-2014, 10:43 PM

Those rubber connectors? Hmmm I've never really looked for them.

These look like them:
Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

Post pictures? You can either upload them to PeachParts as attachments or you can upload them to an image hosting service like imgur: the simple image sharer or Photo and image hosting, free photo galleries, photo editing. I prefer to use imgur as I can make albums like this:

1987 560SL Climate Control Push Button Unit Repair - Imgur

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