Check valve at brake booster line 1985 300D

[mrskemp]

hi everyone,

this is my first post. and it is going to be a long one. i have searched high and low for this answer, hopefully someone here can help me.

background:
i just purchased a 1985 300D, and as part of getting to know this beautiful car, i am going through normal maintenance procedures that i know the previous owner never did.

so, like everyone else, i found a few vacuum issues. first, i discovered leaks in my climate control. chased it to a leaky switchover valve, and a leaky defroster flap pod thingie. no problem, i isolated them and then my car shut off nice and quick and my door locks even work a few days after shutting off car. sweet.

next up was trying to work through wonky shifting problems. searching revealed that to start with, make sure vacuum is good. so, first i cleaned the alda banjo on the manifold, then i put on a vacuum gauge to the line to the transmission just to see that it was being supplied with proper vaccum, but then all hell broke loose, proper vacuum was not showing up anywhere. not even where i had just worked it out. car won't shut off, door locks don't work. uggh.

anyway, after two maddening days that had me checking everything six times over with crazy discrepancies in vacuum everywhere, i think i have figured it out. the second nipple in line on the brake booster line check valve is really slow to build vacuum. but to truly diagnose this problem, i need to know something about this check valve.

to start with, i have attached a vacuum diagram that is my system exactly.

what i have noticed is that my car, which is a W123, and is supposed to have part 140 on the diagram, instead has the W126 check valve, part 140a, which has three nipples instead of two. the third nipple is capped. but do the two nipples in use match exactly between the W123 and the W126? also, if either valve will work, isn't the capped nipple supposed to be at a 180 degrees from the other two? mine is at about 30 degrees. (i have attached a picture of my valve, 140a, the W126 valve)

also, is there a difference between the two nipples? knowing what stock should be from each nipple might be a nice place to start. is the second one 'downstream' (farther away from the vacuum pump) supposed to have a different vacuum reading?

and one more thing, anyone know the color coding of the orifices? i have clear, orange, yellow, and black.


ok. phew. that took a lot.

great forum here, and i look forward to the wisdom that will pour forth.

-carter