I just discovered that the 300TDT and 300SD vacuum systems are quite different and need some help.

The line that goes from the engine vacuum pump to the brake booster has some sort of valve, with a larger sized line that connects on top and goes into the fender well. Next to the valve or as part of the valve there are 2 vacuum male fittings. One seems to supply vacuum the other does not. I assum by someway the valve in the booster line controls this.

There is a clear line (white?) a brown line and a red with a blue stripe.

What is the purpose of the valve in the brake booster line and what is the path of the larger plastic clear line and its purpose?

Does the clear (white) connects to one of the 2 male fitttings on the line and supplies vacuum to the engine vacuum units. Question is which fitting?

Is the solid brown line is the engine shutdown vacuum supply and does it connect to the 2nd male fitting?

Is the red/blue stripe ACC vacuum and does it connet to the 2nd fitting along with the brown?

Thanks for your help.

Don

__________________
1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it

BIGRED,

I can't help with all your questions as I do not have a car of your model and vintage to check. However, the big valve in the line from the vacuum pump to the brake booster is a check valve. Once the motor is shut off the other side of this valve reaches normal atmospheric pressure pretty quickly, and without it you would have no vacuum for braking or other functions when you first got into the car. Hope this helps. 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)

I have a 83 300SD,

1. The valve inline with the brake booster is a check valve with orifice, I do not know where the large clear line that exits the top of the check valve goes to ( my manual is missing at the moment )

2. The vacuum nipple closest to the check valve should have a "T" split, the brown line goes to one side and the red with blue stripe goes to the other.

3. The vacuum nipple furthest from the check valve is for the clear ( white ) line which feeds back towards the engine compartment and tee's to the vacuum switch on top of the valve cover and the other side of the tee goes to the vacuum system damper.

I do not know if your vacuum line schematic label is still intact, when you open the hood it is just to the left of the radiator and above the left headlight, its nice to have in a pinch.

RSH Thank you.

I have the label, but need a better pair of eyes to make it out.

Again, thank you
Don

__________________
1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it