Well, this is what worked for me in my 1981 300tdt.

I am assuming that the vacuum systems for the heat are very similar in other cars...but I may be wrong.

I removed both drivers and passenger side below-dash panels.
Then I turned on the heat to high. Noticed that the vent flaps were all the way up...as if the defrost were on.
I pushed the button next to defrost so that I could at least see what it did to the vents if anything and got nothing. I stuck my hand up there and manually assisted the vents down. Only took a little push to the back of it and down they s-l-o-w-l-y came.
But it DID come down and I had heat pouring out of there. (hold on, not done yet!)

THEN, I pushed the defrost button and they went back up...slow.
Good, I thought, and pushed the button next to the defrost again, and NOTHING! bummer.

Dehind the center console just behind the footwell vent opening on the drivers side is the vacuum pump (I am assuming that is what it is) for those vents.
I wiggled the vac. line at the rubber connector and BOOM! down the vents came, much quicker than the first time. I repeated the defrost, vents go up, but then again they stuck and would not come down on their own. I wiggled the line again and they went back down. I WAS GETTING CLOSER!!!

SO, by process of elimination I replaced the rubber connection to the pump on the drivers side with a 2" piece of rubber tubing...
(drum roll please!)

NOW I HAVE FOOTWELL HEAT!!!!!!!

Consistant and QUICK. It appears that there was some kind of restriction in the original rubber connection, that may or may-not have been there for a reason, as I could not blow thru the original tube. No adverse effects can be seen so far by replacing it with a hollow one. Only good things like FOOTWELL HEAT!
(Even turns off and on automatically based on temp of air coming out!)

Sorry for the long post, but I am very excited to have that problem fixed.

Now onto the locks and hard shifting...

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."

Good job DieselDaddy! I recently replaced one of the changeover valves behind the heat and a/c switches and for the first two days, I had footwell heat. Now it's gone. I have no leaks and I am not all that concerned since it's now May. I will at some point look into it with your post in mind.

__________________
1982 300D Turbo "Helga"
380,000 miles

I'm sure you already know this, but if your locks aren't working, you have a vacuum leak - and that is very likely the cause of your hard shifting. Either that or a vacuum source problem for the tranny vac circuit. Check out this URL for more info:

http://www.continentalimports.com/ser_ic20242.html

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

dieseldaddy,

Sounds like the rubber connector collapsed with age, kind of the opposite of a leak, but a pretty serious impediment to airflow, which stopped your system from working as bad as a leak! Thanks for sharing the solution you devised. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

gsxr,
Thanks for that link!
I just printed it out and will try over the next week to diagnose/tweak. This also answers most of my questions that start with, "What the heck is this...?" VERY detailed info that will help me and others here fix their vacuum systems.
Thanks again!
-Brian

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."

I could feel your excitement bursting through this site!

Fortunately, our climate is warm enough not to have this feature ...

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.