what does the blue vacuum hose that is coming out of the turbo do? on my car (this is not a photo of my car, just a nice example....) this blue hose is not connected (infact, its not even there- must have broke or something) and the rubber L-hose connector to the turbo is not plugged or anything. Does anyone know what the Blue hose does and should I do anything because it is not there on my car?thanks
Scott

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Thanks! Scott
sdpettitt@yahoo.com

Vacuum line to the Air Recirc Valve. You can leave it off, cap both ends, if you can find the other end.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

That's the signal line to the air recirculation valve. MB feels that there are some situations in which it's appropriate to leak boost from the compressor outlet back to the compressor inlet.

I don't know where the signal comes from in an SD but if you're going to leave it disconnected, check the inside of the ARV to make sure the plunger seals properly against the compressor housing port. Otherwise boost will leak and you'll rob yourself of power that's duly yours.

Sixto
95 S420
87 300SDL

looks like a 1985 engine. That was added that specific year, there are slight differences in the CA cars. I believe that blue vac line modulates the turbo outlet. Also the 1985 diesels have an EGR "computer" (well, its an analog module) that feeds some of the emissions stuff as well as driving the tach on the clock in the instrument cluster. That makes for a smoother shifting transmission too.
I never set down to understand how it all operates but its there and the car usually drives fine without it! I believe its fail safe, ie. nothing is prevented from operating properly and causing the car to be inoperative. Very unusual compared to today's electronic nightmares!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Ah yes that's what its called, air recirculation valve. I think its the cause of a certain high pitched noise that all the '85s make and can be cause for concern, not me I always liked it mixed with the whine of the turbo it sort of sounds like a lear jet .

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

thanks guys,
after some more research on the Mshop, now that I know the name of the ARV I have come up with a lot of great info. I think I will pull off the cover to the ARV and permanently lock it shut so it never opens again. anyone want a blue vacuum hose??
thanks
Scott

__________________
Thanks! Scott
sdpettitt@yahoo.com