300D Turbo vacuum "issues."

[DrEntropy]

First time here, first Benz, too. Found her at the convenience store(!) back in September. Now she is ~intermittantly~ refusing to shut down. I have had a v-gauge on the system, but NOT as the problem is showing. Seems to have a "relationship" with the climate control, but even that is guessing... I've downloaded the WONDERFUL diagrams posted here and want to thank those responsible for the info!

Hoping to be a contributing member in future, but for now it's gonna be lurk 'n learn.

[Pete Burton]

get a miti-vac or similar device that has a handle you can sueeze to create and then measure vacuum. Then, connect it directly to the vacuum operated device on the very end(rear facing) of the injection pump. The miti-vac should be able to shut off an idling engine this way. If it does, this is OK. You may have a vacuum leak under the dash, like the hoses going to the ignition switch.

[tangofox007]

Originally Posted by DrEntropy

Seems to have a "relationship" with the climate control, but even that is guessing.

That's reasonable. There are several vacuum actuators in the climate control system. If one leaks when actuated in a particular configuration (ie: heat on) it can "rob" vacuum needed to shut off the engine. In a different configuration, that actuator might not be receiving vacuum and not cause a problem. On some models, it is not uncommon for the engine to shut down with the doors locked, but not unlocked, for example.

[DrEntropy]

The show so far:

Have the pump, Pete: That's what I've done and all's well at the IP. The climate control module ckecks ok, but found two of the solenoids inop, so replaced them. Diverter/flap "motors" seem to be a question now, as sometimes the A/C will blow thru the center vents, sometimes thru the defrost vents... not real anxious to tear out the console et al just now, as after the solenoid swap and subsequent "test," a large mud wasp nest seems to have dislodged from ~somewhere~ under the dash! Passenger footwell had big chunks of it scattered about. Looks like there may be some "non-technical" stuff causing some of the problem ;-} Also the front passenger door lock is "dozy" , so checked the "tees" and junctions under pass. side carpet/flooring... no prob there. All appears to be under that dash or at the passenger door lock motor... Sheesh. Are the lock motors the same as the Audi units of the same period? Just curious at this stage. Will go "deeper" at the weekend. THX for the insight TF007.

[psfred]

You have classic "old benz" vacuum issues. The door actuators have four diaphrams each (none in the drivers's door) that crack and leak, the rubber connectors on the hard plastic lines leak, and the plastic lines in the engine compartment can get brittle from head and hydrocarbon exposure.

What I would do is check each system for vacuum integrity. There are four lines that connect the the main vac line from the vac pump to the brake booster -- brown in the shutoff, white is engine/tranny/EGR supply, yellow is door locks, and green is climate control. Disconnect one at a time and apply vac to the line. Door locks and climate control have reservoirs, so it will take many pumps of the hand pump to pull a vac, but it should so accumulation of vac as you go. If not, it's got a fairly large leak. You will have to trace them down one at a time.

For the shutoff, check the servo itself, the diaphram eventually goes. If it's bad, it will pull engine oil into the keyswitch and that will need to be replaced, so don't mess about too long.

New door lock diaphrams are available for $5 or so each from several places, it's worth replacing them all.

Peter