Awesome news Uro! Thanks!

Some pix:

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URO Parts online catalog: https://apaindustries.com/catalog

Good to see it's in production again ! .

********.com has it too .

Just yesterday I stumbled across the check valve alone and can't recall where .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Update: FYI still out of stock.

I have a question. For the turbo diesel 300D brake booster vacuum hose, the two nipple check valve type, the nipple with the white ring base (0.6 coded) will freely pass air when blowing through it or drawing on it.
The second nipple, black base, and farthest from the brake booster ( 0.5 coded) does not pass air freely (or at all by mouth) either way. I have two of these assemblies and they act the same.

How does the system work? How does the check valve interact with each individual nipple?? In other words,what is the mechanical function of each nipple having different restriction codes?



Thanks. I am trying to figure this out academically.

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Kind of an odd way to look at it because I don't know if there is a such thing as a flow of vacuum. What I am going to call a flow of vacuum comes from the brake booster and goes towards the vacuum pump. So, the check valve with the built in plastic nipples has the check valve not doing anything to the vacuum at the nipples.

If I remember correctly the check valve is to allow you some few brake applications if you lose vacuum. The check valve sort of crates a small vacuum reservoir between it and the booster.

Differences between the flow of the individual nipples I don't know about except that they go to different areas of the vacuum system.

I have the one with 2 nipples and somewhere between the vacuum valve on the fuel injection pump that controls the vacuum to the transmission modulator and the main line there is a plastic restricted fitting inside of the line.

Some of the older models only have a single plastic nipple.

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84 300D, 82 Volvo 244Gl Diesel

Thanks Diesel911, your insight makes sense.

Yet there seems to be a mechanical difference between the two nipples.

So directionality does exist since the two nipple check valve does have an arrow designated "to motor" for proper installation.

The difference between 0.5 and 0.6 does not seem extreme, that is why I am befuddled about the 0.5 black nipple not allowing pressure by mouth as the 0.6 white nipple does.

I can't figure out because at this point I am not educated on the actual vacuum behavior designed for that 0.5 black nipple.

Anybody?

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Correct ;

The check valve causes residual vacuum pressure to remain inside the big brake booster can for 'emergency' use .

The .05 nipple should be open but slightly harder to blow / such through ~ for this reason I use it for the V.C.V. on the injection pump as I don't often want much vacuum going to the tranny's modulator .

I am not sure if Mercedes says to use this nipple for the tranny vacuum control valve .

If your nipple has any glue around it's base it has been snapped off and repaired, the glue used plugged the nipple and you can ever so gently drill it open again is you wish .

In any case, if the white plastic part of the check valve looks chalky, cracked or simply isn't shiny anymore it's toast and is just waiting to snap and cause no vacuum at all, I'd buy a new vacuum pipe before you get stranded .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

There is a picture of a vacuum diaphragm. In the upper left corner it shows the nipple closet to the brake booster check valve as being a restricted orifice and goes in particular to the door lock circuit. The other items that connect to the 3-way rubber connector are not shown.

The other nipple is listed as going to the transmission shift (modulator) system. However, on mine that part of the circuit has a restricted orifices inserted into the line and according to the manual that is supposed to reduce the vacuum to a certain amount that I cannot remember.
https://www.pinterest.com/pin/224476362663302238/

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84 300D, 82 Volvo 244Gl Diesel

My own main line had been repaired. I broke the nipples off on the first oil change I did.

In the crowded picture you see the front nipple with the yellow dashed line goes to the vacuum valve on the fuel injection pump that controls the vacuum to the transmission modulator.

The read dash line comes off of the nipple nearest the check valve and it goes to the door locks and one other item. I think the other item is it supplies the vacuum to the vacuum shutoff valve on the steering column lock. But, I am not entirely sure on that.

The green line with the red stripe I believe goes to the climate control vacuum pods.

The yellow circle is where the restricted orifice is in the line. Mine is reddish brown and I have seen are green or yellow I am guessing depending on the size of the orifice.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

I like "The Jungle" .

Reminds me of the rats nest of wires behind the headlight on some Motocycles .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks vwnate1 and diesel911, it is a puzzle coming together.

Interesting that the 1979 240D diagram seems to indicate a brake booster line with two nipples. My 1979 300D's brake booster line only has one separate check valve and one 'open' nipple separate from the check valve.

haha I also liked the "Jungle" note on that spaghetti.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

My feeling is the .05 aperture nipple was for the V.C.V. simply because you want less vacuum to the modulator .

As you mentioned, Mercedes came up with the idea of color coded restrictors to make quick and easy changes but I've not seen any of those in some years .

They also made a multiple arm vacuum spider that has more arms than the usual ones, I sadly lost the part number, it was used to adapt a single nipple vacuum pipe .

The main thing here is to understand what you're doing, then you can fix the problems and after that fine tune it to where you like it .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks vwnate1,that makes alot of sense.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

URO Parts Brake Hose/Line; Brake Booster/Servo Line with 2 Vacuum Connections at Check Valve | 1234307429

$58 on sale at an online source near you. In stock !

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

FWIW :

I put one of these on my 240D some years back and it's still going strong .

Well worth the $ IMO .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better