80 300D Vacuum Nightmare - PeachParts Mercedes-Benz Forum

paul46 · #1 11-16-2006, 01:42 AM

Changed the oil yesterday and ended up with a couple vacuum lines that didn't seem to go anywhere. I then printed a vacuum line diagram from a post that Sam from CA posted, and printed out the instructions from Brian in NY post for removing lines that are for the ERG. With my papers in hand I began to tackle the problem. I didn't get very far when I realized nothing I had matched my engine. You can see from the pics that modifications were made before. I had a heck of time replacing the oil filter with the linkage and valve in the hose in the way.

After changing the oil it wouldn't shift at all until it reach a high rpm.
so I found a lose line and plugged it into an available hole. Now it shifts but too soon. It goes through all gears without enough rpms, resulting in a very slow acceleration. It used to shift hard but at the right time.

Since I've owned the car for about 9 months now, it won't shut off if the defroster is on. It still does that as well.

There were several problems that I've fixed just by reading and searching the forums and the diy stuff available. I replaced the voltage regulator after several months of charging the battery every other day, what a difference! Thanks guys! It still has a few other electrical problems also that I won't address here.

She starts real well and runs real well, no smoke hardly! I get about 27mpg. Only paid $800 for it.

Can you make out if I have the lines going to right places or not? The black line on top of the valve cover goes to the trany.

Speaking of the valve cover there seems to be some oil coming out of the cap which is new problem since the oil change. Could it be the 5W 30 oil I put in is too thin and causing blow by?

I'm trying to keep this to the point but there are so many questions I would like to ask. Thanks for your help? I'm having a great time with these cars and projects.

mbdoc · #2 11-16-2006, 08:54 AM

ONE thing in the 1st picture is the plastic on/off vacuum valve at the top of the valve cover...... the plastic "lever" that depresses the metal pin on the valve is bent away from that metal plunger.. that plastic lever needs to be able to depress that plunger!

paul46 · #3 11-16-2006, 02:01 PM

Thanks so much M.B.Doc. It was only partially contacting the metal plunger about half way. I bent it back up to fully depress the plunger and drove it.

It now seems to shift at the correct time. Amazing that something that small could make such a big difference. I also noticed that if the throttle linkage is pushed to full open (while engine was stopped) that the metal pin could hold the throttle open. That would be very bad if you stomped on the gas and it stuck to full open while driving! Is it possible to remove the whole plastic thing with the pin and everything on top of the valve cover? It seems it would be much simpler and safer.

I also noticed that the pulsating vibration that I've felt while driving mostly between 45 and 55 mph seemed to be much more pronounced. I think it has something to do with the tranny not the engine. Maybe it too has to do with vacuum?

Thanks again for your help.

vstech · #4 11-16-2006, 02:31 PM

I'll take a pic of my 80 TD set of lines... not sure if they are right, but it might help.
John

rhodes2010 · #5 11-16-2006, 03:01 PM

I drive the 1980 300D.

As pointed out the lever on the valve on your valve-cover needs to be intact.
You can buy the lever separately from Fastlane (or your dealer) without having to buy the whole valve.
If the valve leaks, replace it. It is well worth it.

I will get some pictures of my configuration and post them.
It looks like you got it all though.

You may be experiencing the unique nature of these particular cars -
if you use the accelerator gradually the tranny shifts quickly, sort of bogging
the engine. I tend to drive more pedal to the floor and this causes the engine
to wind up to higher RPM's and cause later shifts. It is all in the driving technique.

At first I was overwhelmed by the 1980 vacuum arrangement and did not think I would ever figure it out.
Then (now) I realized how tremendously simple it is. You'll get it.

The 1980 has a simple transmission setup that works really well.
I have more trouble with the later turbo with bowden cable than I do this earlier model.