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LinkBack | Thread Tools | Display Modes |
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#1
09-10-2015, 07:10 PM
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300SEL/M103 smoking like crazy, line to vacuum return modulator full of tranny fluid
Well the title of the post pretty much says it all. I was on the freeway and started to notice billowing clouds of gray smoke following me. It got worse every time I touched the gas pedal. My first thought was - oh crap - head gasket or valve seal issues, but after reading some threads here, I took a look at the vacuum line going to the transmission modulator, and sure enough it's full of red transmission fluid.
Am I correct to assume that replacing the modulator and changing the fluid is what's needed, or is there anything else I should be on the lookout for? And what's a good source for a new modulator? Big thanks in advance! ThePhoenix 
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#2
09-10-2015, 08:24 PM
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Interesting. I thought only the diesels had a modulator at the tranny.
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#3
09-11-2015, 10:06 AM
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I think you got the modulator and diesel thing mixed up, the unique item in your MB diesel that can control the modulator on the transmission is the vacuum control valve on the injection pump. It bleeds off vacuum gently as you press the accelerator pedal.
This mimics the function of the intake manifold losing of a gasoline engine losing vacuum as the throttle plate is opened up. The problem this user is having is not new, modulators are known to go bad in this way. There are dozens of such incidents on the internet, and usually identified by gasoline engine benz owners because of the smoke that happens.
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2012 BMW X5 (Beef + Granite suspension model) 1995 E300D - The original humming machine (consumed by Flood 2017) 2000 E320 - The evolution (consumed by flood 2017)
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#4
09-11-2015, 10:09 AM
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Got it; thanks. And the modulator makes it go from a very soft shift to a firm shift the more clicks you turn it - I think - counterclockwise?
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#6
09-17-2015, 05:47 PM
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Quote:
It is right on the driver side of the transmission with a vacuum line running to it. About the size of a golf ball. They can also fail causing full line pressure shifts at low throttle input, BTDT.
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I'm not a doctor, but I'll have a look.  '85 300SD 245k '87 300SDL 251k '90 300SEL 326k Six others from BMW, GM, and Ford. Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]
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