vaccum crazy - PeachParts Mercedes-Benz Forum

roe · #1 03-08-2004, 06:30 PM

85 300D help where do you start how many vacuums are there??? door locks stuck-motor run for 10-15 sec when you shut off-trans shifts hard-Is this my nightmare-where to start. Hi I'm new HELLO everyone new to diesel

#2 03-08-2004, 08:11 PM

Would be helpful to supply us with the year and model of the car in question.
By the way, don't panic yet, and welcome to the Forum. My impression of what you have would be either a vacuum pump that has gone bad, or just a vacuum leak. There are plenty of places to leak vacuum on these cars. They are usually in the door locking mechanisms and are not that hard to repair.
But first, tell us about your car.

kerry · #3 03-08-2004, 09:54 PM

Did you just change the oil? Lots of people dislodge a vacuum line when removing the oil filter.

dmorrison · #4 03-09-2004, 03:29 AM

Welcome to the forum.

#1 buy a Mityvac vacuum tester. Or equivilent
This is a good price (below). Or get it locally

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=2068

#2 As was posted. You may have knocked a vacuum line loose.
did the vacuum problems happen all of a sudden, IE you knocked something loose or has it slowly been getting bad.?

#3 Here is a link to a service manual for your style car.

http://skinnerbox.steaky.org/123_DISK2/program/123-cd-index.html

The items that use vacuum on the W123 body style Mercedes, which is the body style for the 300D, are as follows.

Door/fuel flap/trunk lock vacuum elements.
Air Conditioning flap actuators.
Brake booster
Injection pump shut off.
EGR valve control
Transmission shifting signal

Look at the vacuum hoses carefully. Check for cracked, hard plastic lines. Check the connection of the hard plastic line into the rubber connections. Is it a good connection? Separate one and see how easily it separates. It should be a firm connection, Its should hold vacuum. try a couple to get a feel for it. Check the rubber straight connectors, 3way rubber connectors and 4way rubber connectors. Is the rubber in poor condition?
Check the connections on the top of the valve cover. This black covered unit has some air switch valves that send signals to the transmission and EGR valves. Again look and check all the lines, rubber and connections in the engine compartment.
Just to the left of the brake booster ( facing towards the back of the car) are the lines that enter the cabin for the AC system, door locks and shutoff control. You can disconnect these and plug the connectors (golf tees work in the rubber part) in the engine compartment ( DO NOT DISCONNECT the brown and brown/blue hard plastic lines that is the shutoff system. Lets keep that associated with the engine compartment) . Your pluggin the engine side of the tubes not the tubes going into the cabin. Make sure you keep track of what went where. This will isolate the AC and door locking system from the engine components. When you do this how does the car shift and how does it shut off. No improvement/ then the problem is in the engine compartment. If it operates fine then the problem is either the door locks or AC vacuum elements.
For that I will refer you to the Service Manual web site and job numbers

80-010 tru 902 covers the door locking system

83-54 covers the vacuum elements.

07.1-150 The shutoff switch inside the car and on the injection pump

When reconnecting the vacuum lines that go into the cabin, The various systems can be added one at a time. That way you know the problem system. The various hard plastic lines are color coded to identify the system, IE brown and brown/blue go to the vacuum shutoff control switch attached to the ignition switch.

Look at what was been suggested and get back to us with the results.

Dave