Owners Manual VS Mechanic ... Who to believe?
 

Issue #1 )
Hello there everyone, I have a 1981 300TDT Wagon which I recently purchased. While browsing through the ORIGINAL manual I noticed a page on cold starts. In the manual it says that on cold morning to depress the gas pedal 1/2 the way down and then when you turn the key to start the motor, to hold they key down to the right until the car begins to run without knocking.

I asked a mechanic at a non factory MB shop about this and he said no, just prime the glow plugs twice.

Issue #2) I thought my car had a vacuum leak because the power locks will lock or unlock if the car was recently turned off, but if left overnight, only the driver side will unlock/lock. Car shows no other signs of a vacuum leak.

The same mechanic said that they were meant to be like this and that it does not constitute a vacuum leak.

search for a different mechanic. glowing the plugs twice is good advice, on COLD COLD mornings, by this I mean turn on the key count to 30, or listen for the glow plug relay to click off, Ignore the light, then turn the key off, and back on and count to 30 again. then immediatly start it. I also recommend giving it part throttle until the idle smooths out.
doors are designed to be lock/unlockable for days with the car off, and should cycle 5 or 6 times with the car off. othewise look for a leak.

get another mechanic.

This one is blowing smoke up your..............

Stop calling him a mechanic!

"Man who looks at cars"

Give the guy a break! He obviously isn't a Diesel MB guy. He could be a great Toyota, or Ford mechanic. Just becuase is isn't a MB guru like the folks around here, doesn't make him a bad mechanic. That said I too would suggest a different mechanic. Find one that know MBs, and if you can find one that knows diesel MBs even better.

You should be able to lock and unlock you door locks many times without problems. If you can't you have a vac leak somewhere.

For cold starting most of the time all you have to do it give the car an extra glow cycle or two and she should fire right up.

Few mechanics are familiar with the Mercedes anti-theft systems. There is a photoelectric sensor hidden in the rear windshield. When is senses that the sun has set, it opens a valve which dumps the vacuum in the door lock reservoir, making it more difficult to enter the vehicle without the proper key, thereby providing additional security during the hours of darkness. For security reasons, details of this system were intentionally omitted from all service manuals and electrical schematics.

WHAT WHAT WHAT???? uh, which vehicles are equipped with this?
from what I understand ALL cars over about 150K miles "aquire" this "security feature"... no sensor required!

Glowing twice on cold mornings is good. So is depressing the pedal a bit. Both good things to do. Locks should always unlock and that means leak. However if it takes 8 hours to leak its probably not worth worring about and maybe thats that the mechanic is trying to tell you by beating around the bush. In which case he is probably a keeper as he isn't trying to jack you for a leak that takes 8 hours to leak.

I've been looking through some recently declassified CIA documents and apparently Mercedes considers this feature to be a "Theft Annoyance". By dumping the vacuum, when a thief and his buddies break into your car, he cannot just open the locks for everyone automatically, he must go around to every lock and manually unlock it.

Many a thief has expressed their hatred of Mercedes for their "Thief Annoyance" features.