i'm in the process of tracking down a vacuum leak so my car will shut off and my doowr will lock....so far i've determined that the leak is coming from somewhere inside the car....i've noticed a hissing sound coming from behind the push button panel for the heater in my 82 300D...at first i didn't think this was related to my doors not locking because it has been doing this for weeks....

so i took off the panel,, started the car,,, and tracked down the hiss to something that i think was refered to as a "pod"....when i stuck my finger over this the center vents came on... So should I plug this and see what happens???? would this cause my transmission to shift hard too, as it does now....

Yes, vacuum leaks can cause hard shifts. Plug the line to the pod for the moment and see what happens. This could the sole source of your problem since as long as the climate control is on, it would draw down the vacuum. A simple test for the leak is to shut off the climate control and see how the doors work then. If the doors work fine the climate control off, the leak is in the climate control. Also try driving it with the climate control off and see if the shifts improve.
You're still going to need the MityVac though.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I have a leaking pod too - haven't traced it yet, but shutting off the AC a few seconds prior to turning off the engine assures the vacuum cutoff works and allows my doors to lock properly. I guess it didn't seem worth tearing into when all it took to "fix" was turning off the AC

John

__________________
John Hughes, was in Landstuhl, Germany but currently in San Antonio, TX


1978 280CE Astral Silver now 59,xxx miles and counting "Silber-Kugel"
1986 300E Black Pearl Metallic 143,xxx miles 5-spd daily driver w/ blk leather "Schwarz-Schönheit"
1989 190E 2.6 (euro) 5-spd Desert Taupe 112,xxx kms Had to leave behind in Germany!!! "Helga"
1983 300D Pastel Beige now 312,xxx + miles SOLD

OBK#24

Okay...when i sit in the car with it running and lock and unlock the doors nothing happens....but when i cover the hissing hole "the pod right?" with my finger the locks work well as does the engine shut off...the hole i cover is the second one from the left and labeled with a #3....can i just change this individual pod or is it more involved than that? or can i just plug it up with something??? Also, i get the same effect when i turn the heater contol to the cold position...

also when i shut the car off there is another faint burst of air that sounds like a small vacuum leak when the hole is cover....also this doesn't help with the transmission shifting issue...still shifts hard...

thanks for the help tracking this thing down...

The pod is a device about an inch and a half in diameter, attached to an activation device which opens and closes the vents. It sounds to me as if you may be referrring to a switchover valve. There are a row of switchover valves behind the climate control panel. If this is what is the problem, changing the switchover valve should solve part of your problem.
You're still going to need a MityVac to check the amount of vacuum in the system to see if your hard shifts are caused by a vacuum problem.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

kerry edwards....thanks for all your help....yeah...you're right on the money...it's one of switches in the row of valves behind the climate control buttons...

Are you sure the vacuum line hasn't just fallen off the barb on switchover valve #3? I'm assuming that's what you're covering with your finger. See if there is a loose line around there.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

There is a hissing sound coming from behind my push button panel. With a little help from the forum I determined that it was a switch over valve (the row of valves mounted behind the push botton panel) I went to the junkyard today and pulled a few off an old 82' 300D, replaced mine and its still leaking air out of the bottom (actually it's more of a suction). When it is on heat there is no leaking or hissing sound. When i turn the blower off it starts hissing, until i turn the temp. control all the was down to cold. I'm pretty sure this is the cause of my vacuum woes. Can someone help me figure this thing out? What else should I replace?

Also, I have an extra push botton panel so i switched them out and I have the same problem.

__________________
1985 Mercedes 300DT

I am getting the same thing happening. Did you ever find a solution? Does anybody know about this?

I have seen several people post about it, but not much info out there.