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#1
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Hissing sound in dash
There is a significant hissing sound (obviously vacuum related) in my dash that varies according to engine rpm. It is especially noticable just after a shift and sounds like a 'release' of vacuum at that time. Also, if I hold the accelerator such that I am just before a shift point, a constant hiss is heard. This is on the '84 300TD.
Any suggestions on what this might be before I tear into the dash?
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1985 MBZ 300DT 1969 MBZ 220d 1984 MBZ 300TDT 1981 VW Vanagon |
#2
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Strange you mention that. I have the EXACT same thing on my 84 Euro 300D (They stuck a turbo on it in Germany).
I always wondered what it could be.. I assume it has to do with either the transmission pressure release, or the Turbo, but I have no clue. |
#3
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Is your Euro an auto? My guess is that it is transmission related... question for forum members: is the 'dash pot' (aka surge damper) located under the dash? I thought this was under the hood...
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1985 MBZ 300DT 1969 MBZ 220d 1984 MBZ 300TDT 1981 VW Vanagon |
#4
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I *WISH* it was a 5spd. =\ |
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Stuck a turbo on it? Its not a turbo engine? What kind of boost?
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http://superturbodiesel.com/images/sig.04.10.jpg 1995 E420 Schwarz 1995 E300 Weiss #1987 300D Sturmmachine #1991 300D Nearly Perfect #1994 E320 Cabriolet #1995 E320 Touring #1985 300D Sedan OBK #42 |
#6
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I have the answer:
The hissing sound is normal, thats the transmission shiftpoint-valve-vent-line. Its a little black vacuum line that just ends inside the dash (so it sucks in cleaner air) and when you let off the throttle it causes the valve to draw air through that line, thus the hissing sound. Its normal, mine does it too when I am coasting. I kinda like it though.
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-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#7
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Very, VERY low boost. Whoever did it appears to have been intelligent enough not to screw up the engine. From what I understand, they modified the valves properly, and toyed with the IP, before sticking the thing in there. Even then, they dont have it cranked up very high.. since the car is still only slightly faster than a 240D.
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#8
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Quote:
__________________
1985 MBZ 300DT 1969 MBZ 220d 1984 MBZ 300TDT 1981 VW Vanagon |
#9
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Quote:
__________________
-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#10
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I suggest you do a test or two...
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IF it turns out to be the "Vent" line from the Vacuum Control Valve [VcV] mounted on the rear of the IP... IF this is the source of this noise, I would most certainly put a cheap paper fule filter on this line where it terminates under the dash... this way it will not suck in dust/dirt and cause a problem with your Engine/Tranny vacuum control system under the hood. I have the kick panels off both of our 1980(s) and you canNOT hear the vacuum when shifts occur on either of these cars. Regards, |
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