1987 300D Turbo...slow to shut down
 

Hello all,

I have a 1987 300D Turbo that's a bit slow to shut down...I have also noticed that it doesn't seem to be shifting (automatic) quite properly.

Do these events have a connection?

Upon a quick inspection under the hood, I found no vacuum lines disconnected.

My first thought would be the vacuum fuel shutoff in the injection pump...Is that difficult to replace?

Any suggestions would be appreciated.

The Tenor Man

Try capping off (one at a time) the climate control vacuum lines, and the door locks.

Those tend to leak a lot.

Leak
 

I had a leaky vacuum actuator in the coupe's passenger door. The car started not shutting down when the vacuum leak got bad enough.

And yes, vacuum leaks could affect shifting if bad enough.

One thing I noticed was that the system would build vacuum and behave normally when the doors were locked. But in the un-locked position it would not hold vacuum.

So, Out with the Mighty-Vac, which I used to test vacuum circuits from under the hood. Found the reservoir to be good. Confirmed the leak when the doors were un-locked.

I then removed the driver's door panel so I could access the lock and un-lock circuits at the switch in the door. This may have been un-necessary, but it did allow me to verify that the switch itself was not leaking.

I by-passed all the trunk actuators and still had the leak, which localized it to the door. Opened the door and found the rubber boot on the actuator's rod to be cracked.

I scored another actuator from a '84 sedan in the scrap yard, installed, and all is well again. I noticed that MB changed the design of that boot, and also upgraded to a silicone-based material that won't crack as easily.

The idea is to find which system leaks, and then remove devices from the system to localize the leaky item.

Hope this helps!

Sounds like a vacuum issue with both problems related. I don't know how the vacuum system is set up on non-123 cars. Shut off valve is not hard to replace on a 617 but the problem is usually elsewhere in the system on 123's. A quick test is to put a Mity Vac or your lips on the vacuum line to the shut off valve, pull a vacuum and see if it shuts off promptly. If it does, the shut off valve is ok and you have a leak elsewhere.

Thanks...1987 300D Vacuum System
 

I was under the understanding that on the 124 chassis, the door, trunk and fuel door vacuum system was operated by the vacuum pump under the rear seat. If so, I could rule out the locking system as the culprit.

I thought that the climate control and engine vacuum was getting its vacuum from the main pump on the front of the engine (which I upgraded to the latest version in July, 2007).

Anyone know?

Thanks,
The Tenor Man

You are correct, sir, although I'm pretty sure your pump is in the spare tire well of your trunk - unless you have a wagon. 123s are quite different from 126s and 124s in this respect.

You are correct on all counts Tenor, and yes, the pump for the door locks (and orthopedic seats if installed) is under the RR seat on the wagon and sedan 124.

- Jeff

Tenor, There are several possibilities, but it would appear that the root cause of your issue is VAC. improper vac to the shut-off valve will cause a your delay and improper shifting. Some of the possibilities include, the check valve (black and white plastic piece located on the drivers side near the fire-wall) or the connecting vac lines. or even the shut off valve itself. unfortunately the engine vac system is all tied together, so in reality the leak could be elsewhere.

Do you own a mighty vac tool?

This could help you track down any leaks

FWIW the temp gauge for the EGR on mine was the cause of a very hard to find vac leak.
-nB

:confused::confused:

Thermal vacuum valve, maybe??

Something like that. It went EGR -> this thingy -> black box on valvecover.