Vaccum problems on a w116 300SD

[Teradoc]

Hi everyone, first time poster here.

I've have a high milage(somewhere around 500k, not exactly sure though) 1979 300SD, my dad gave it to me awhile back, and I've been using it as a daily driver. It has a few problems though, and I'm hoping someone can help me out a bit.

First, I assume there is a vaccum leak, because the doors will lock under power, or within a minute or so of when I turn the car off, but after that minute, I have to unlock the doors by hand, or start the car, and the building vaccum unlocks them.

Second, sometimes it wont shut off right away, it seems that I have to let pressure build up to trigger the shut off. I assume this is part of the vaccum problem.

Third, its having transmission problems, the shifting is not smooth, it will go to shift, and then hang in nuetral for a second or so, I have to release the gas right when it shifts, and resume throttle once it finishs. Also, the reverse has stopped working, not completly, but its as if the clutch is slipping really badly or somthing, it acts as if it is in nuetral, but, if its on a flat surface, it will start to move backwards, slowly. I found a transmission for it, and I'm just wondering if it can be fixed, is it part of the vaccum problem, or if I do need a new tranny.

Fourth, it burns oil if I get the RPM's up over 3200 or so, it stopped doing it as bad since I put higher viscosity oil in 20-50, and recently I put Syntec, and it's been doing much better. I assume this is because the oil is being thrown out the oil vent, and is pushed through the turbo. And I was planning on putting a stage 2 intake kit from http://www.wade************************/ in to fix the problem. Will that work?

This car is old, has a lot of miles on it, but in 5 years, it has never broken down, it does foul plugs, but its the early series of motor, and I was told that they tend to do that. It's been very good to me, and now, its time to freshen it up a bit, breathe some life back into it. (The only irritating thing is, people like to steal the hood emblem)


I hope this list isnt too long or anything, and thanks for whatever help you guys can offer.

[Apodman]

Check your ATF level. Make sure you check it with the engine running. If low, don't over-do the refill. Take it one Dixie Cup measure at a time.

Hope this helps.

[300SDog]

On the vacuum issue, slow engine shut down tells you it's not just a leak at one of the doorlock diaphrams.

The vac pump on front of the engine has its own diaphram inside the housing. Cost is about $40 for a rebuild kit. And blowing oil through a cracked vac pump diaphram into the intake manifold is a symptom the pump needs a rebuild - increased oil consumption.

Eyeball the lines and connections too, but dont get lost unplugging and reattaching vac lines. And i think there's a vacuum solenoid sensor for the tranny too....... so replacing the vac pump diaphram might solve all your problems, oil consumption, tranny shifting, door locks and engine shut down.

[Aaron]

On the slow shut off problem, it could also be the vac shutoff switch at the ignition switch or also shutoff diaphragm at rear of injection pump.

As for the locks, you most certainly have either a leaking element or leaking line. Only way to diagnose is to go step by step, through the doors, trunk lid and fuel flap to see where the leak is.

I am surprised to hear that the car doesn't use the Syntec oil as fast as it did with dino oil. It's usually the other way around. That also goes for leaks.

What do you mean by "fouling plugs"? Glow plugs don't have the same life cycle as spark plugs do.

[Teradoc]

The ATF level is fine, and by fouling plugs, I mean, I usually go through 1 or 2 a year.

[Teradoc]

A little update, I traced down a major leak to the vacuum resivoir in the trunk, just fixing that, several problems dissapeared. it shuts off right now, and shifts a little better too. Next step is rebuilding the vacuum pump.