Won't Shut Off / Vac. Leak Somewhere???!!!
Thanks for looking at this post. I am having time of it diagnosing a system of problems...

1985 300TDT 176k or so. Need to know what parts of the vac sys need to be adjusted or replaced - for the first 10-20 mins of driving, until it reached about 80c or so...the tranny clunks as it downshifts back to first at 17mph. This condition stops however if the a/c (which mostly works, sometimes) is on. Having the a/c on also makes the power locks work much better (well, not to mention that the vacuum reservior has been replaced by a 4.5 gal tank for holding diesel for startups and cool downs - runnin on SVO the rest of the time - main tank conversion)(pretty cool, too). But the vac res there or not doesnt change the fact that the locks work when the a/c is on. When the tranny is warm, the downshifts are smooth, a/c or not.

Until yesterday, when I decided to plug what i thought was the leak. There is a part, which probably needs replacing, that apparently at some point had been sealed because it has a leak. It is the component that kind of looks like a blue and white fishing bob. I thought a little tape wouldnt hurt, but after i did it - the locks wont work at all, the a/c does not smooth the downshifts, and I have to use the stop button to shut off the car (which i of course do before i shut off the ignition as not to put an extra load on the alternator). the only other thing i did was extend one portion of the throttle linkage 4 turns because it seemed like there hadnt been enough power in the pedal. i dont think that is what caused the sudden loss of bac system

So - I hope this is specific enough for someone to poinnt me to a post or something that would help figure out what is going on with my car.
Thanks for your time...

Glenn

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1981 300TDT 250K+
1985 300TDT 174K

It sounds like you have a vacuum leak in one of the pods for the HVAC system.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Here is a link that should be posted as a "sticky note".
82 300TD A/C problem

There is a 10 step process typed out that explains how to look for a vacuum leak.

Here is another link
1985 300D Vacuum leak

It gives a very brief description of your vacuum system.

And yet another link
Center vents problem

What kind of shape are the underhood vacuum lines in? Easy enough to replace, use a three foot length of quality vacuum hose.

I failed to mention the shut-off valve on the IP.

You do have a MityVac????

I do have one. one of the first things i bought when i bought the 1981 before I traded it for the fuel system modification.

and by the way...these problems exist no matter what fuel i am running,m so i know the main tank conversion didn not affect the vac system (well, except for removing the vac reservior. The only thing this affected was that the doors don't unlocm or lock when the car is not on.

I will probably just bypass the lock system because i dont really like it - i just need to get a master key for the car bacause i only got the valet key which doesnt open the tailgate.

thanks for your help so far. great links

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1981 300TDT 250K+
1985 300TDT 174K

I found a big hole in the "check valve" i think. its the first component in the line out of the break booster with the arrows pointing the direction of flow out of the booster. it differs from the diagram that I saw of the 82 in that it actually has a hose connected to it that goes into another T (more of an X). appears to be the main line too, so no vac is working properly. All i need to figure out is what this part is called so i can get another one. i'll check fastlane to see if i can find it. OK...thanks...

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1981 300TDT 250K+
1985 300TDT 174K

I found a big hole in the "check valve" i think. its the first component in the line out of the break booster with the arrows pointing the direction of flow out of the booster. it differs from the diagram that I saw of the 82 in that it actually has a hose connected to it that goes into another T (more of an X). appears to be the main line too, so no vac is working properly. All i need to figure out is what this part is called so i can get another one. i'll check fastlane to see if i can find it. OK...thanks...

That would be the brake booster hose, one screws onto the brake booster and the other end screws onto a pipe coming off your vacuum pump. Common part to fail after 20+ years, and will cause the problems mentioned in your original post. The "X" you are talking about feeds other components of the vacuum system. Alan

I get it now....the valve is part of the whole hose mechanism...and of course it is a 50 dollar hose. Well...buymbparts is here in GA, so lets hope the jb weld holding the broken part holds up enough to go get the replacement hose.

So - thanks for your help...a lot. Anyhow - do you know of a vac hose/connector replacement kit, or do i have to buy a bunch separately. the '85 vac syst, as you know, is quite involved and a bit over engineered. But its still a great car.

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1981 300TDT 250K+
1985 300TDT 174K

When you replace the vacuum hose, check and see if it is free of oil. Oil in the vacuum hose indicates vacuum pump failure. Remember it comes off a pipe that attaches to the vacuum pump, be careful when removing the line, as not to kink the pipe.

All your connectors will have to be purchased separately. You need to count the number of vacuum tees required, three and four port. As for the vacuum hoses shaped like elbows, I would use high quality, thick wall vacuum hose. Buy a three foot length, that should be more than enough to replace all the connections. You can purchase the elbows individually, it's more cost effective to use a length of hose when replacing several.

Your 300D is an '85 model? Check the plastic vacuum lines leading to the turbo, EGR, transmission transducer (blue saucer beside brake booster) and shut-off valve. I may have missed a few others. The plastic vacuum line is available in bulk, it is not color coded.

Rusty should have everything at his store in GA, never been there, talked to him over the phone many a time. It turns out our paths may have crossed many years ago in the parts room.

Sometimes I miss my 240D, such a simple car to repair!!!!!

There are a few diagrams on the discussion board that may help. I do have the pdf file that was missing from version 1 CD set, covering the ACC system. It was sent to me last year by another user in the discussion forum. I had a set of paper manuals, and should of Xeroxed them ##$%^#)%%!!!!

I am interested in your progress, post it on the discussion board for all to see!!!!!

Alan